CIE iGCSE Co-Ordinated Science P1.5.1 Effects of forces Exam Style Questions Paper 3
Question
(a) Fig. 6.1 shows two horizontal forces acting on a truck as it moves forwards along a flat, level road.
(i) Calculate the magnitude of the resultant horizontal force on the truck.
Draw an arrow on the diagram to show the direction of the resultant force.
magnitude = …………………………………………….. N
(ii) Describe the motion of the truck as the resultant force is applied.
…………………………………………………………………………………………………………………….
(b) The truck has two identical headlamps.
The lamps are connected in parallel across a 12V battery. One switch turns on both lamps. A fuse protects the circuit.
(i) Fig. 6.2 shows an incomplete circuit diagram for this circuit
Fig. 6.2
Complete Fig. 6.2 using standard electrical symbols.
(ii) State one advantage of connecting the lamps in parallel.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(iii) Complete the sentences about the fuse.
The purpose of a fuse is to ………………………………………………… the circuit. A large
……………………………….. in the circuit causes the fuse to get hot and melt, breaking the circuit.
▶️Answer/Explanation
Ans : 6(a)(i) 500 (N) ;
arrow to the left / forwards ;
6(a)(ii) accelerates (forwards) / owtte ;
6(b)(i) lamp symbol correct ;
all other symbols correct ;
lamps connected in parallel ;
all else correct ;
6(b)(ii) both lamps get full voltage / if one lamp stops working, the other still works ;
6(b)(iii) protect ;
current ;
Question
(a) Fig. 9.1 shows four forces acting on a submarine.
The submarine is moving underwater from right to left.
(i) State which force A, B, C or D is the weight of the submarine.
……………………..
(ii) Force B has the same magnitude as force D.
Describe the motion of the submarine.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(b) The submarine is powered by a small nuclear reactor.
In the nuclear reactor, energy is released by the nuclear fission of an isotope of uranium.
(i) Describe what happens to an atom during nuclear fission.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………..
(ii) Ionising radiation is released in the reactor during nuclear fission.
Suggest why the nuclear reactor is surrounded by a thick layer made of lead.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(c) Ultrasound waves have a frequency higher than the maximum audible frequency for a human.
(i) The submarine uses ultrasound waves to calculate the depth of the water below the submarine.
A pulse of ultrasound is sent through the water and reaches the sea floor after 0.8s.
Ultrasound waves travel through seawater at a speed of 1550m/ s.
Calculate the distance of the sea floor below the submarine.
distance = …………………………………………….. m
(ii) Ultrasound waves are not part of the electromagnetic spectrum.
State the name of one region of the electromagnetic spectrum and give one use for waves in this region.
name …………………………………………………………………………………………………………………
use ……………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans : 9(a)(i) C ;
9(a)(ii) (moving at) constant speed ;
9(b)(i) nucleus ;
splits ;
9(b)(ii) Stop the escape of / provide better shielding from ionising radiation OWTTE ;
9(c)(i) distance = speed × time (in any form) or 1550 × 0.8 ;
= 1240 (m) ;
9(c)(ii) region ;
correct use ;
Question
(a) A farmer drives his tractor in a field.
Fig. 6.1 shows the forces J, K, L and M acting on the tractor as the tractor accelerates towards the right.
(i) State which force J, K, L or M is the weight of the tractor.
………………………….
(ii) Explain why force K must be greater than force M.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(b) Fig. 6.2 shows a speed‐time graph for the tractor as it travels across the field.
(i) Describe the motion of the tractor during the section PQ.
…………………………………………………………………………………………………………………….
(ii) Calculate the distance travelled by the tractor during section QR.
distance = …………………………………………….. m
(c) The tractor pulls a tank full of water.
The mass of the water is 2500kg.
The density of water is 1000kg/m$^{3}$.
Calculate the volume of the water.
volume = ……………………………………………. m3
(d) Suggest two renewable sources of energy that the farmer uses to generate electricity for the farm.
1 ………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 6(a)(i) L ;
6(a)(ii) resultant force needed to cause acceleration / change in speed (to the right) ;
6(b)(i) tractor has constant acceleration ;
6(b)(ii) distance = speed×time (in any form) or 6×70 ;
= 420 (m) ;
6(c) volume = mass / density (in any form) or 2500/1000 ;
= 2.5 (m$^{3}$) ;
6(d) wind ;
solar ;
Question
(a) (i) Fig. 3.1 shows a skier standing on the snow.
When she stands on the snow without her skis, she sinks into the snow.
When she wears her skis, she can stand on the snow without sinking.
Explain these observations.
(ii) The skier makes a sound near a high wall.
The sound travels through the air as a wave.
The skier hears an echo.
State what happens to the sound wave at the high wall to cause an echo to be heard.
(b) Fig. 3.2 shows the forces acting on the skier on level snow when she is travelling in a snowmobile.
(i) State which force, J, K, L or M, is the weight of the snowmobile and skier.
(ii) State which force, J, K, L or M, is the friction force acting on the snowmobile.
(c) Fig. 3.3 shows the speed–time graph for the motion of the skier.
(i) State the maximum speed of the skier.
speed = …………………………………………. m / s
(ii) The skier is accelerating during the first 20 s of her journey.
Describe how the graph shows that the skier is accelerating.
(iii) Show that the distance travelled by the skier during the first 20 s is 50 m.
(d) The skier is exposed to ultraviolet radiation from the Sun.
Ultraviolet radiation is a form of ionising radiation.
Describe one danger to humans of being exposed to large quantities of ultraviolet radiation.
▶️Answer/Explanation
Ans : 3(a)(i) skis increase surface area ;
pressure is less with skis ; ORA
3(a)(ii) sound wave is reflected ;
3(b)(i) L ;
3(b)(ii) K ;
3(c)(i) 5 (m / s) ;
3(c)(ii) line has a slope / gradient ;
3(c)(iii) area under graph or ½ × 5 × 20 ;
3(d) skin cancer ;
Question
(a) Fig. 6.1 shows an athlete running on a level road.
Four forces A, B, C and D act on the runner.
Force B is the driving force which moves the athlete forward.
State the names of forces C and D.
C …………………………………………………………………………
D …………………………………………………………………………
(b) Complete the sentence to describe how forces change a body.
Forces may change the direction of motion of a body,
the …………………………………………………………………. of a body
and the …………………………………………………………………. of a body.
(c) The athlete runs up a hill at constant speed.
Use words or phrases from the list below to complete the sentences about the energy transfers taking place. Each word or phrase may be used once, more than once or not at all.
chemical potential gravitational potential
kinetic light
Stored …………………………………………………… energy from food is
transferred to …………………………………………………… energy as the athlete moves.
As the athlete moves up the hill his store of …………………………………………………… energy increases.
The speed of the athlete is constant when moving up the hill, so his …………………………………………………… energy remains constant.
(d) Explain why the athlete’s power output is greater when he runs faster.
(e) A photographer takes a photograph of the athlete using a digital camera with a thin converging lens as shown in Fig. 6.2.
Two rays of light are shown passing from the head of the athlete to the lens.
(i) A focused image of the athlete’s head is formed on the image sensor.
Complete Fig. 6.2 to show how these two rays pass from the lens to form the image on the sensor.
(ii) On Fig. 6.2, draw a double headed arrow (↔) to show the focal length of the lens.
(iii) Circle two words or phrases that describe the image formed.
diminished enlarged inverted
same size upright
▶️Answer/Explanation
Ans : 6(a) C weight ;
D drag / air resistance ;
6(b) Any two from size ;
shape ;
speed ;
6(c) chemical potential kinetic gravitational potential kinetic;
6(d) rate of work done increases;
6(e)(i) ray 1 refracts through F and meets ray 2 on the image sensor ;
ray 2 continues in a straight line onto image sensor ;
6(e)(ii) focal length correctly shown ;
6(e)(iii) inverted ;
diminished ;
Question
(a) Fig. 9.1 shows two different car tyres.
A car driver observes that her car sinks into soft ground when she uses tyres X. She changes the tyres on her car to Y, so that it does not sink into the soft ground.
Explain why tyre Y will cause less pressure to be exerted on the ground than tyre X.
(b) A thermometer is used to measure the temperature of the air in a tyre.
Fig. 9.2 shows a simple liquid-in-glass thermometer.
(i) State the name of the temperature scale used in the thermometer in Fig. 9.2.
(ii) The liquid in the thermometer is alcohol.
State the physical property of alcohol that varies with temperature used in this thermometer.
(iii) State the two physical properties that define the fixed points on this temperature scale.
1 …………………………………………………………………………
2 …………………………………………………………………………
(c) Fig. 9.3 shows two horizontal forces acting on a car as it moves along a straight road.
(i) Calculate the size and direction of the resultant horizontal force on the car.
size of resultant force = ……………………………………………………………………………….
direction of resultant force …………………………………………………………………………
(ii) The driver of the car applies the brakes to slow the car.
Fig. 9.4 shows the force from the driver’s foot on the brake pedal.
Calculate the moment of the force from the driver’s foot about the pivot.
moment = ………………………………………… Ncm
▶️Answer/Explanation
Ans : 9(a) any one from greater surface area (in contact with ground) ;
same force acts over a larger area ;
9(b)(i) celsius ;
9(b)(ii) volume ;
9(b)(iii) melting point of ice / freezing point of water (0) ;
boiling point of water (100) ;
9(c)(i) 350 (N) ;
to the right / forward ;
9(c)(ii) moment = force × (perpendicular) distance or formula or 40 × 18 ;
= 720 (N cm) ;
Question
(a) Fig. 3.1 shows four forces acting on a submarine. The submarine is moving underwater at a constant speed.
State which force A, B, C or D is the weight of the submarine. (Sub-topic – P1.5.1)
▶️Answer/Explanation
Answer: C
Explanation: The weight of the submarine is the force due to gravity acting downward. In the diagram, force C is directed downward, indicating that it represents the weight of the submarine.
(b) The submarine travels 36 km in 2 hours. Calculate the speed of the submarine in m/s. (Sub-topic – P1.2)
▶️Answer/Explanation
Answer: 5 m/s
Explanation:
- Convert 36 km to meters: \( 36 \text{ km} = 36,000 \text{ m} \).
- Convert 2 hours to seconds: \( 2 \text{ hours} = 2 \times 60 \times 60 = 7,200 \text{ s} \).
- Calculate speed using the formula \( \text{speed} = \frac{\text{distance}}{\text{time}} \): \( \text{speed} = \frac{36,000}{7,200} = 5 \text{ m/s} \).
(c) The submarine is powered by a small nuclear reactor. Ionising radiation is released in the reactor. The reactor must be shielded to protect the crew from this radiation. (Sub-topic – P5.2.2)
(i) State how exposure to ionising radiation can affect the human body.
▶️Answer/Explanation
Answer: Cancer / cell mutation
Explanation: Ionising radiation can damage the DNA in cells, leading to mutations that may cause cancer or other harmful effects on the body.
(ii) Suggest a material which can be used to shield a nuclear reactor and stop \(\alpha\)-radiation and \(\beta\)-radiation escaping.
▶️Answer/Explanation
Answer: Lead
Explanation: Lead is a dense material that is effective at blocking \(\alpha\) and \(\beta\) radiation due to its high atomic number and density.
(d) Plutonium-239 (Pu-239) is the nuclear fuel used by the submarine. Pu-239 has a half-life of 24,000 years. A small sample of Pu-239 has a mass of 1.0 g. Calculate the mass of Pu-239 remaining after 96,000 years. (Sub-topic – P5.2.4)
▶️Answer/Explanation
Answer: 0.0625 g
Explanation:
- Determine the number of half-lives in 96,000 years: \( \frac{96,000}{24,000} = 4 \) half-lives.
- Calculate the remaining mass after each half-life: \( 1.0 \text{ g} \rightarrow 0.5 \text{ g} \rightarrow 0.25 \text{ g} \rightarrow 0.125 \text{ g} \rightarrow 0.0625 \text{ g} \).
(e) When it is under the water, the submarine uses a periscope to view a ship on the surface of the sea. Fig. 3.2 shows a simple periscope.
On Fig. 3.2, draw a ray of light from the ship to the observer’s eye to show what happens to the light ray as it passes through the periscope. (Sub-topic – P3.2.1)
▶️Answer/Explanation
Answer: The light ray should reflect off the top mirror and then the bottom mirror before reaching the observer’s eye.
Explanation: In a periscope, light from the ship enters the top mirror, reflects downward to the bottom mirror, and then reflects into the observer’s eye. The ray should be drawn to show these two reflections.
Question
(a) Water vapour in the air over the sea comes from liquid water in the sea.
(i) State the name of the process by which liquid water in the sea forms water vapour in the air.
…………………………………………………………………………………………………………………….
(ii) Describe how the process named in (i) occurs. Use ideas about water molecules in your answer.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(b) Fig. 6.1 shows a boat moving at constant speed.
Four forces A, B, C and D act on the boat.
State the name of force C.
…………………………………………………………………………………………………………………….
(c) Fig. 6.2 shows a speed-time graph for the boat.
(i) Determine the speed of the boat.
speed = …………………………………………. m/s
(ii) Calculate the distance travelled by the boat in 200s.
distance = …………………………………………….. m
(d) Fig. 6.3 shows a wave similar to a water wave on the surface of the sea.
(i) Determine the wavelength of the wave.
wavelength = …………………………………………….. m
(ii) On Fig. 6.3, indicate with a double headed arrow (↕ or ↔) the amplitude of the wave.
(iii) The frequency of the wave is 0.08Hz.
Calculate how many wavefronts pass a fixed point in 25 seconds.
▶️Answer/Explanation
Ans: 6(a)(i) evaporation
6(a)(ii) fastest moving/most energetic molecules/particles ;
escape from surface ;
6(b) Weight ;
6(c)(i) 4.4 (m/s) ;
6(c)(ii) distance = speed × time (in any form symbols or words) or 4.4 × 200 or area under graph ;
880 (m) ;
6(d)(i) 8 (m) ;
6(d)(ii) amplitude correctly indicated ;
6(d)(iii) 2.0 ;
Question
(a) Fig. 9.1 shows a rocket about to be launched.
(i) The weight of the rocket is 8000000N.
When the rocket is launched, the upward force exerted by the rocket is 12000000N.
Calculate the resultant upward force on the rocket.
resultant force = …………………………………………….. N
(ii) Explain why the resultant force cannot be zero, when the rocket is launched.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(iii) The rocket travels 385000km from the Earth to the Moon in 75 hours.
Calculate the average speed of the rocket in km/ s.
speed = ………………………………………… km/s
(b) An astronaut on the rocket uses a telescope to view a star.
Fig. 9.2 shows a lens that is used in the telescope. Light rays from the star pass through the
lens and are focused at the principal focus.
(i) On Fig. 9.2, label the principal focus of the lens with the letter F.
(ii) On Fig. 9.2, draw a double headed arrow ( ↔ ) to indicate the focal length of the lens.
(iii) State the name of the process that occurs when light passes into the lens and the direction of the light changes.
…………………………………………………………………………………………………………………….
(c) The astronaut communicates with Earth using radio waves.
(i) Place radio waves in the correct place in the incomplete electromagnetic spectrum shown in Fig. 9.3.
Fig. 9.3
(ii) State which part of the electromagnetic spectrum has the greatest frequency.
…………………………………………………………………………………………………………………….
(iii) Explain why it is not possible for the astronaut to use sound waves to communicate directly with Earth.
…………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 9(a)(i) 4 000 000 (N) ;
9(a)(ii) rocket would not, move/take off ;
9(a)(iii) conversion of 75 hours to seconds / 270 000 s ;
speed = distance ÷ time or substituted distance ÷ time ;
speed = 1.43 (km/s) ;
9(b)(i) principal focus correctly identified ;
9(b)(ii) focal length correctly identified ;
9(b)(iii) refraction ;
9(c)(i)
9(c)(ii) $\gamma$- rays ;
9(c)(iii) there is no medium / there is a vacuum ;
no particles to transfer the vibrations (preventing sound from travelling) ;
Question
Fig. 9.1 shows an aircraft at rest on a runway.
(a) The mass of the aircraft is 400 000 kg.
Calculate the weight of the aircraft. The gravitational field strength, \( g \), is 10 N/kg. (Topic – P1.3)
▶️Answer/Explanation
Weight = 4,000,000 N
Explanation: Weight is calculated using the formula \( W = m \times g \), where \( m \) is mass and \( g \) is gravitational field strength. Substituting the values, \( W = 400,000 \, \text{kg} \times 10 \, \text{N/kg} = 4,000,000 \, \text{N} \).
(b) The aircraft starts from rest and accelerates along the straight runway. The aircraft engines produce a constant horizontal thrust force of 1,200,000 N. A constant frictional force of 500,000 N acts on the aircraft. (Topic – P1.5)
(i) Calculate the resultant horizontal force acting on the aircraft.
▶️Answer/Explanation
Resultant force = 700,000 N
Explanation: The resultant force is calculated by subtracting the frictional force from the thrust force: \( F_{\text{resultant}} = 1,200,000 \, \text{N} – 500,000 \, \text{N} = 700,000 \, \text{N} \).
(ii) Explain why the aircraft accelerates.
▶️Answer/Explanation
The aircraft accelerates because there is a resultant force acting on it.
Explanation: According to Newton’s Second Law of Motion, an object accelerates when there is a resultant force acting on it. In this case, the resultant force of 700,000 N causes the aircraft to accelerate.
(c) Fig. 9.2 shows a TV monitor in the cabin of the aircraft and the energy transferred each second by the monitor.
(i) The number of joules of sound energy transferred per second is shown as XJ. Calculate the value of X. (Topic – P1.6)
▶️Answer/Explanation
X = 1 J
Explanation: The total energy input is 200 J, and the energy outputs are 119 J (light) and 80 J (thermal). Therefore, the sound energy \( X = 200 \, \text{J} – (119 \, \text{J} + 80 \, \text{J}) = 1 \, \text{J} \).
(ii) The monitor has a resistance of 1900 Ω. The current passing through the monitor when in use is 0.060 A.
Calculate the potential difference across the monitor. State the unit of your answer. (Topic – P4.2)
▶️Answer/Explanation
Potential difference = 114 V
Explanation: The potential difference (V) is calculated using Ohm’s Law: \( V = I \times R \). Substituting the values, \( V = 0.060 \, \text{A} \times 1900 \, \Omega = 114 \, \text{V} \).
(iii) The current of 0.060 A is the same as 60 mA. The fuse in the electrical supply to the monitor has to be replaced. Several fuse ratings are available.
10 mA 50 mA 100 mA 250 mA
State which fuse is the correct choice. Explain your answer. (Topic – P4.4)
▶️Answer/Explanation
Fuse = 100 mA
Explanation: The fuse rating should be higher than the maximum current (60 mA) but not too much higher to ensure safety. A 100 mA fuse is the most appropriate choice as it is the smallest value above 60 mA.
Question
(a) A person standing on a warm, sunny beach is exposed to several forms of electromagnetic radiation.
Fig. 12.1 shows part of the electromagnetic spectrum.
Complete Fig. 12.1 by writing the names of the other two forms of electromagnetic radiation in the correct places.
(b) The person stands with both feet on some very soft sand on the beach.
When one foot is lifted off the sand, the other foot sinks deeper into the sand.
Explain why this happens.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(c) A sample of sand has a mass of 8000kg.
This sand has a density of 1600kg/m$^{3}$.
(i) Calculate the volume of this sample of sand.
volume = …………………………………. m$^{3}$
(ii) Show that the weight of this sample of sand is 80000N.
The gravitational field strength, g, is 10N/kg.
(d) A piece of glass has been left on the beach. The glass acts like a convex lens focusing the Sun’s rays.
Fig. 12.2 shows two rays of light passing through a convex lens.
(i) Complete the light rays in Fig. 12.2 to show how the light rays are focused by the lens.
(ii) State the name of point F.
…………………………………………………………………………………………………………………….
(iii) On Fig. 12.2, draw a double headed arrow (↔) to indicate the focal length of the lens.
▶️Answer/Explanation
Ans: 12(a)
microwaves in correct place ;
X-rays in correct place ;
12(b) area decreases ;
so pressure increases ;
12(c)(i) volume = mass / density (in any form symbols or words) or 8000 / 1600 ;
= 5 (m$^{3}$ ) ;
12(c)(ii) 8000 × 10 ;
(= 80 000 N)
12(d)(i) rays meet at focus (F) ;
Question
12. (a) (i) State which force is the weight of the bus in Fig. 12.1.
▶️Answer/Explanation
Answer: R
Sub-topic Code: P2.1 (Forces)
Detailed Solution: The weight of the bus is the force acting vertically downwards, which is represented by force R in Fig. 12.1.
12. (a) (ii) Force Q is 500,000 N. State the size of force S.
▶️Answer/Explanation
Answer: 500,000 N
Sub-topic Code: P2.1 (Forces)
Detailed Solution: Since the bus is traveling at constant speed, the forces are balanced. Therefore, force S (air resistance) must be equal to force Q (engine force), which is 500,000 N.
12. (b) The bus uses stored chemical energy from fuel to accelerate up a hill. Some of this energy is transferred to thermal energy and sound energy. State two other forms of energy transferred to the bus as it accelerates up the hill.
▶️Answer/Explanation
Answer: kinetic energy; gravitational potential energy
Sub-topic Code: P3.1 (Energy Transfers)
Detailed Solution: As the bus accelerates up the hill, its kinetic energy (due to motion) and gravitational potential energy (due to height) increase.
12. (c) State the method of thermal energy transfer between the Sun and the Earth.
▶️Answer/Explanation
Answer: radiation
Sub-topic Code: P4.1 (Thermal Energy Transfer)
Detailed Solution: Thermal energy from the Sun is transferred to the Earth by radiation, which does not require a medium and can travel through the vacuum of space.
12. (d) Describe one difference between the magnetic properties of soft iron and the magnetic properties of steel.
▶️Answer/Explanation
Answer: iron magnetises quicker / iron loses magnetism quicker
Sub-topic Code: P11.1 (Magnetism)
Detailed Solution: Soft iron magnetizes and demagnetizes more quickly than steel, making it suitable for temporary magnets, while steel retains magnetism for longer.
12. (e) Name one other non-renewable energy source and one renewable energy source.
▶️Answer/Explanation
Answer: coal / natural gas; hydroelectric / solar / tidal / waves / geothermal / biogas / wind
Sub-topic Code: P3.1 (Energy Resources)
Detailed Solution: Non-renewable energy sources include coal and natural gas, while renewable energy sources include hydroelectric, solar, tidal, waves, geothermal, biogas, and wind energy.
12. (f) Describe how the motion of the molecules inside the tyres changes as the air warms up.
▶️Answer/Explanation
Answer: gain KE / move faster
Sub-topic Code: P4.1 (Thermal Properties)
Detailed Solution: As the air inside the tyres warms up, the molecules gain kinetic energy and move faster, increasing the pressure inside the tyres.
Question (a)
An astronaut travels to the Moon in a spacecraft. The weight of the spacecraft at take-off is 25,000,000 N. When the spacecraft blasts off from Earth, it is pushed upwards by a force of 32,000,000 N.
Calculate the resultant upward force on the spacecraft.
The resultant upward force can be calculated by subtracting the weight of the spacecraft from the upward force applied during take-off.
▶️Answer/Explanation
Answer: 7,000,000 N Explanation: The resultant upward force is calculated as follows: \[ \text{Resultant Force} = \text{Upward Force} – \text{Weight} \] \[ \text{Resultant Force} = 32,000,000 \, \text{N} – 25,000,000 \, \text{N} = 7,000,000 \, \text{N} \] Therefore, the resultant upward force on the spacecraft is 7,000,000 N.
Question (b)
The spacecraft has solar panels to gather energy from the Sun. This energy is stored in batteries on the spacecraft.
(i) Complete the sentences to describe the energy conversion that takes place in this process.
The Sun’s light energy is transformed into electrical energy by the solar panels. This energy is stored as chemical potential energy in the batteries.
▶️Answer/Explanation
(ii) Solar energy is a renewable energy source. State one other renewable energy source.
One other renewable energy source is wind energy.
▶️Answer/Explanation
Answer: Wind energy Explanation: Wind energy is a renewable energy source that harnesses the kinetic energy of wind to generate electricity using wind turbines. It is sustainable and does not deplete natural resources.
Question (c)
(c) The spacecraft travels 386,000 km from Earth to the Moon in 72 hours. Calculate the average speed of the spacecraft in km/s.
To calculate the average speed, divide the total distance traveled by the total time taken, converting hours to seconds.
▶️Answer/Explanation
Answer: 1.49 km/s Explanation: First, convert 72 hours into seconds: \[ 72 \, \text{hours} = 72 \times 60 \times 60 = 259,200 \, \text{seconds} \] Then, calculate the average speed: \[ \text{Average Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{386,000 \, \text{km}}{259,200 \, \text{s}} \approx 1.49 \, \text{km/s} \] Therefore, the average speed of the spacecraft is approximately 1.49 km/s.
Question (d)
On Earth, the astronaut has a mass of 80 kg and a weight of 800 N. On the Moon, the astronaut has a mass of 80 kg and a weight of 135 N. Describe the difference between mass and weight.
Mass is a measure of the amount of matter in an object and is constant regardless of location. Weight is the force exerted on an object due to gravity and varies depending on the gravitational field strength.
▶️Answer/Explanation
Answer:
Mass is the actual amount of material contained in a body (measured in kg or g).
Weight is the force exerted by gravity on that object.
Explanation: Mass is an intrinsic property of an object and does not change with location. Weight, however, depends on the gravitational force acting on the object. On the Moon, the gravitational field strength is weaker than on Earth, so the astronaut’s weight is less, even though their mass remains the same.
Question (e)
The astronaut communicates with Earth using radio waves.
(i) Fig. 12.1 shows an incomplete electromagnetic spectrum.
Place radio waves in the correct place in Fig. 12.1.
Radio waves should be placed in the right-hand box of the electromagnetic spectrum, as they have the longest wavelength and lowest frequency.
▶️Answer/Explanation
Answer: Radio waves in the right-hand box. Explanation: The electromagnetic spectrum is arranged in order of increasing frequency and decreasing wavelength. Radio waves have the longest wavelengths and lowest frequencies, so they belong on the far right of the spectrum.
(ii) Explain why it is not possible for the astronaut to communicate with Earth using sound waves.
Sound waves require a medium (such as air, water, or solids) to travel through. In space, there is no medium, so sound waves cannot propagate, making communication using sound waves impossible.
▶️Answer/Explanation
(iii) Fig. 12.2 shows a sound wave. On Fig. 12.2, label with a double-headed arrow (↔) one wavelength of the sound wave.
One wavelength of the sound wave can be labeled by drawing a double-headed arrow from one peak to the next peak or from one trough to the next trough.
▶️Answer/Explanation
Answer: Double-headed arrow from peak to peak or trough to trough. Explanation: The wavelength of a wave is the distance between two consecutive peaks (crests) or troughs. Labeling this distance with a double-headed arrow indicates one complete cycle of the wave.
Question (a)
Fig. 12.1 shows the horizontal forces acting on a motorcyclist and his motorcycle.
(i) Calculate the resultant horizontal force acting on the motorcyclist and motorcycle.
Force: ………………………………………….. N
(ii) Describe how this resultant force changes the speed of the motorcycle.
▶️Answer/Explanation
Answer:
(i) Resultant force: 300 N
(ii) The resultant force causes the motorcycle to slow down.
Explanation: (i) The resultant force is calculated by subtracting the backward force (e.g., friction or air resistance) from the forward force (e.g., engine thrust). For example, if the forward force is 500 N and the backward force is 200 N, the resultant force is 500 N – 200 N = 300 N. (ii) A resultant force in the opposite direction of motion (backward) acts to decelerate the motorcycle, reducing its speed.
Question (b)
Fig. 12.2 shows a speed-time graph for the motorcycle’s journey over 80 s.
(i) State a time when the motorcycle is not moving.
………………………………………….. s
(ii) On Fig. 12.2, label with the letter C a point when the motorcycle is moving at a constant speed.
(iii) On Fig. 12.2, label with the letter S a point when the speed of the motorcycle is increasing.
▶️Answer/Explanation
Answer:
(i) The motorcycle is not moving at 0 s, 40 s to 45 s, or 80 s.
(ii) Label a point between t = 15 s and t = 30 s or between t = 60 s and t = 70 s with the letter C.
(iii) Label a point between t = 0 s and t = 15 s or between t = 45 s and t = 60 s with the letter S.
Explanation: (i) The motorcycle is stationary when the speed is zero, which occurs at the start (0 s), during a pause (40 s to 45 s), and at the end (80 s). (ii) Constant speed is represented by a horizontal line on the speed-time graph. This occurs between 15 s and 30 s or between 60 s and 70 s. (iii) Increasing speed is represented by an upward-sloping line on the speed-time graph. This occurs between 0 s and 15 s or between 45 s and 60 s.
Question (c)
The motorcycle produces a loud sound with a high frequency when moving.
Describe the pitch and amplitude of the sound waves produced.
Pitch:
Amplitude:
▶️Answer/Explanation
Answer:
Pitch: High
Amplitude: Large
Explanation: – Pitch is determined by the frequency of the sound wave. A high-frequency sound corresponds to a high pitch. – Amplitude is related to the loudness of the sound. A loud sound has a large amplitude.
Question (d)
As the motorcycle moves along the road, the temperature of the air in the tyres increases.
Explain why the pressure of the air in the tyres increases.
▶️Answer/Explanation
Answer:
increased kinetic energy / speed (of molecules) ;
more frequent collisions with tyre ;
Explanation: According to the kinetic theory of gases, an increase in temperature causes gas molecules to gain kinetic energy and move faster. This results in more frequent and forceful collisions with the walls of the tyre, leading to an increase in pressure.
Question
(a) Fig. 9.1 shows a wind surfer on a surfboard, driven by the wind, sailing at a constant speed across the water.
Four forces J, K, L and M acting on the surfboard are shown.
(i) Explain why force K and force M must be equal and opposite.
▶️Answer/Explanation
The surfboard is moving at a constant speed, which means there is no acceleration. According to Newton’s first law of motion, if an object is moving at a constant speed, the net force acting on it must be zero. Therefore, force K (the force of the wind pushing the surfboard forward) and force M (the force of water resistance opposing the motion) must be equal in magnitude and opposite in direction to balance each other out.
(ii) Identify force L.
▶️Answer/Explanation
Force L is the gravitational force or weight acting downward on the surfboard.
(iii) Work is done by the wind to move the surfboard across the water. State the two quantities needed to calculate the work done by the wind.
▶️Answer/Explanation
The two quantities needed to calculate the work done by the wind are:
- The force exerted by the wind (force K).
- The distance over which the force is applied (the distance the surfboard moves).
(b) Fig. 9.2 represents a water wave.
(i) On Fig. 9.2, label the amplitude of the wave with a double-headed arrow (↔ or ↓).
▶️Answer/Explanation
The amplitude of the wave should be labeled as the vertical distance from the equilibrium position to the crest or trough of the wave.
(ii) The waves have a frequency of 0.1 Hz. Explain what is meant by a frequency of 0.1 Hz.
▶️Answer/Explanation
A frequency of 0.1 Hz means that one wave passes a fixed point every 10 seconds. Frequency is the number of complete waves that pass a point per second, so 0.1 Hz corresponds to one wave every 10 seconds.
(c) Water molecules in the sea are able to form water vapour above the sea. During this process, the more energetic molecules escape from the surface of the sea.
(i) Suggest the effect this will have on the energy of the water molecules remaining in the seawater.
▶️Answer/Explanation
The water molecules remaining in the seawater will have less energy on average because the more energetic molecules have escaped as water vapour. This results in a decrease in the average kinetic energy of the remaining molecules.
(ii) Suggest the effect this will have on the temperature of the seawater.
▶️Answer/Explanation
The temperature of the seawater will decrease because the average kinetic energy of the remaining water molecules has decreased. Temperature is a measure of the average kinetic energy of the molecules, so a decrease in kinetic energy leads to a decrease in temperature.
(d) Some seawater has a volume of 5.0 m3 and a mass of 5120 kg. Calculate the density of the seawater.
▶️Answer/Explanation
Density is calculated using the formula:
\[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \]
Given:
Mass = 5120 kg
Volume = 5.0 m3
\[ \text{Density} = \frac{5120 \, \text{kg}}{5.0 \, \text{m}^3} = 1024 \, \text{kg/m}^3 \]
Therefore, the density of the seawater is 1024 kg/m3.
Question
(a) Fig. 12.1 shows a large snow tractor used in Antarctica.
The snow tractor has large continuous tracks. These tracks allow the snow tractor to move across the snow without sinking.
Explain why a tractor with normal wheels would sink into the snow.
▶️Answer/Explanation
Answer: A tractor with normal wheels would sink into the snow because the weight of the tractor is distributed over a smaller surface area, leading to higher pressure on the snow. The large continuous tracks of the snow tractor distribute the weight over a larger surface area, reducing the pressure on the snow and preventing the tractor from sinking.
(b) When gasoline (petrol) burns in the engine of the snow tractor, carbon dioxide gas and water vapour are produced. State which of the diagrams, X, Y or Z in Fig. 12.2, shows the arrangement of gaseous carbon dioxide molecules. Give a reason for your answer.
▶️Answer/Explanation
Answer: Diagram Z shows the arrangement of gaseous carbon dioxide molecules. The reason is that in the gaseous state, molecules are far apart and move freely, which is represented by the widely spaced and randomly arranged molecules in Diagram Z.
12(c)(i) The snow tractor accelerates. State the form of energy gained as the tractor accelerates.
▶️Answer/Explanation
Answer: The form of energy gained as the tractor accelerates is kinetic energy.
12(c)(ii) The snow tractor moves up a hill at constant speed. State the form of energy gained as the tractor moves up the hill.
▶️Answer/Explanation
Answer: The form of energy gained as the tractor moves up the hill is gravitational potential energy.
12(d) Fig. 12.3 shows a distance-time graph for the snow tractor moving at constant speed.
Calculate this constant speed.
▶️Answer/Explanation
Answer: The constant speed can be calculated using the formula: \[ \text{speed} = \frac{\text{distance}}{\text{time}} \] From the graph, the distance covered is 8 meters in 16 seconds. Therefore: \[ \text{speed} = \frac{8 \, \text{m}}{16 \, \text{s}} = 0.5 \, \text{m/s} \]
Question
(a) A farmer uses solar panels to generate the electricity needed for his farm.
Suggest why the farmer should have an alternative method of generating electricity rather than relying on just solar energy.
▶️Answer/Explanation
Solar panels only generate electricity during daylight hours and are dependent on weather conditions. Therefore, the farmer should have an alternative method to ensure a continuous supply of electricity, especially during the night or on cloudy days.
(b) Fig. 6.1 shows the farmer driving his tractor. Four forces, A, B, C, and D, are acting on the tractor.
The tractor is moving at a constant speed. The weight of the tractor is 40,000 N.
(i) State which force, A, B, C, or D, is the weight of the tractor.
▶️Answer/Explanation
Force C is the weight of the tractor.
(ii) Calculate the mass of the tractor. The gravitational field strength, g, is 10 N/kg.
▶️Answer/Explanation
Using the formula \( W = mg \), where \( W \) is the weight and \( g \) is the gravitational field strength:
\( m = \frac{W}{g} = \frac{40,000}{10} = 4,000 \, \text{kg} \).
(iii) Force B is 2,000 N. State the value of force D. Explain your answer.
▶️Answer/Explanation
Force D is 2,000 N. Since the tractor is moving at a constant speed, the forces acting on it are balanced. Therefore, the force opposing the motion (force D) must be equal to the driving force (force B).
(c) The tractor uses diesel fuel. State the form of energy stored in the diesel fuel.
▶️Answer/Explanation
The form of energy stored in diesel fuel is chemical (potential) energy.
(d) The farmer drives his tractor across a field. Fig. 6.2 shows the speed-time graph for the tractor.
(i) State the maximum speed of the tractor.
▶️Answer/Explanation
The maximum speed of the tractor is 2.0 m/s.
(ii) On Fig. 6.2, mark with an X a time when the tractor is moving with changing speed.
▶️Answer/Explanation
An X should be marked at any time between 0 and 5 seconds or between 15 and 20 seconds, as these are the periods when the speed is changing.
(iii) Calculate the distance travelled by the tractor between time = 15 s and time = 20 s.
▶️Answer/Explanation
The distance travelled can be calculated by finding the area under the speed-time graph between 15 s and 20 s. The shape is a triangle with a base of 5 s and a height of 2 m/s:
\( \text{Distance} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 5 \times 2 = 5 \, \text{m} \).