Question 1 (Sub-topic – 1.2)
Fig. 1.1 shows the speed–time graph for a cyclist beginning a race. The motion of the cyclist changes at points A, B and C.
(a) Using information from Fig. 1.1, determine:
(i) the speed of the cyclist at time = 6.0 s
(ii) the maximum speed of the cyclist.
▶️Answer/Explanation
(i) Speed at 6.0 s: From the graph, at time = 6.0 s, the speed is 3.0 m/s.
(ii) Maximum speed: The maximum speed is 16 m/s, which occurs at the highest point on the graph.
(b) (i) Describe the motion of the cyclist between point A and point B.
▶️Answer/Explanation
The cyclist is accelerating (speed is increasing) between point A and point B.
(ii) Describe how the motion of the cyclist between points B and C differs from the motion between points A and B. Give a reason for your answer.
▶️Answer/Explanation
Difference: The cyclist has a greater acceleration between points B and C compared to between points A and B.
Reason: The gradient of the speed-time graph is steeper between points B and C, indicating a greater acceleration.
(c) Determine the distance travelled by the cyclist between point A and point B.
▶️Answer/Explanation
The distance travelled is the area under the speed-time graph between points A and B. The area is a triangle with a base of 5 s and a height of 10 m/s.
\[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 5 \times 10 = 25 \, \text{m} \]
Therefore, the distance travelled is 25 m.
Question 2
(a) State the principle of conservation of energy. (Sub-topic – 1.7.1)
▶️Answer/Explanation
The principle of conservation of energy states that energy cannot be created or destroyed, but it can only be transformed or transferred from one form to another. This means that the total amount of energy in a closed system remains constant.
(b) Fig. 2.1 shows the energy flow diagram for a car powered by a petrol engine.
(i) Using the information in Fig. 2.1, calculate the percentage of energy transferred from the chemical store to the kinetic store. (Sub-topic – 1.7.1)
▶️Answer/Explanation
The chemical energy store is 100%, and the kinetic energy store is 30%. Therefore, the percentage of energy transferred from the chemical store to the kinetic store is 30%.
(ii) Fig. 2.2 shows the energy flow diagram for an electric car. The electric car is driven by an electric motor which is powered by a battery. (Sub-topic – 1.7.1)
Using the information in Fig. 2.1 and Fig. 2.2, state which car is more efficient. Give a reason for your answer.
▶️Answer/Explanation
The electric car is more efficient because it transfers a higher percentage of energy from the chemical store to the kinetic store (70%) compared to the petrol car (30%). This means less energy is wasted as internal (thermal) energy and sound in the electric car.
Question 3
A platform rests on a pivot as shown in Fig. 3.1.
A diver sits at a distance of 1.8 m from the pivot. The weight of the diver is 1100 N. (Sub-topic – 1.5.2)
(a) Using the information in Fig. 3.1, calculate the moment of the diver about the pivot.
▶️Answer/Explanation
Solution:
The moment of a force is calculated using the formula:
\[ \text{Moment} = \text{Force} \times \text{Perpendicular distance from the pivot} \]
Given:
– Force (Weight of the diver) = 1100 N
– Distance from the pivot = 1.8 m
\[ \text{Moment} = 1100 \, \text{N} \times 1.8 \, \text{m} = 1980 \, \text{N m} \]
Therefore, the moment of the diver about the pivot is 1980 N m.
(b)(i) Fig. 3.2 represents the platform without the diver. (Sub-topic – 1.5.2)
The moment of the weight \( W \) of the platform is balanced by the moment of the spring. The spring exerts a downward force of 62 N.
Using the information in Fig. 3.2, calculate the weight \( W \) of the platform.
▶️Answer/Explanation
Solution:
The principle of moments states that for an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments.
Given:
– Force exerted by the spring = 62 N
– Distance of the spring from the pivot = 1.2 m
– Distance of the weight \( W \) from the pivot = 0.4 m
\[ \text{Moment of the spring} = \text{Moment of the weight} \]
\[ 62 \, \text{N} \times 1.2 \, \text{m} = W \times 0.4 \, \text{m} \]
\[ 74.4 \, \text{N m} = 0.4 \, \text{m} \times W \]
\[ W = \frac{74.4 \, \text{N m}}{0.4 \, \text{m}} = 186 \, \text{N} \]
Therefore, the weight \( W \) of the platform is 186 N.
(ii) The graph of load against extension for a spring is shown in Fig. 3.3.
The unstretched length of the spring is 16 cm.
Determine the length of the spring when the load on the spring is 240 N.
▶️Answer/Explanation
(length of spring =) 17 (cm)
(extension =) 1.0 (cm)
Question 4
A student holds a pile of books. The mass of the books is 3.2 kg.
(a) Calculate the weight of the books. (Sub-topic – 1.3)
▶️Answer/Explanation
Answer: 31 N
Explanation: The weight of an object is calculated using the formula: \[ \text{Weight} = \text{mass} \times \text{gravitational field strength} \] Given: \[ \text{mass} = 3.2 \, \text{kg}, \quad \text{gravitational field strength} = 9.8 \, \text{m/s}^2 \] Therefore: \[ \text{Weight} = 3.2 \times 9.8 = 31.36 \, \text{N} \] Rounding to two significant figures, the weight is 31 N.
(b) The student carries the books from the bottom to the top of the stairs shown in Fig. 4.1.
The vertical height of the stairs is 4.5 m. (Sub-topic – 1.7.1)
(i) Show that the work done on the books when they are carried to the top of the stairs is approximately 140 J.
▶️Answer/Explanation
141(.12) (J) OR 139(.5) (J)
3.2 × 9.8 × 4.5 OR 31.36 × 4.5 OR 31 × 4.5
(work =) force × distance OR (W =) F × d
(ii) Determine the gravitational potential energy gained by the books. Give a reason for your answer.
▶️Answer/Explanation
Answer: 141 J
Explanation: The gravitational potential energy (GPE) gained by the books is calculated using the formula: \[ \text{GPE} = \text{mass} \times \text{gravitational field strength} \times \text{height} \] Given: \[ \text{mass} = 3.2 \, \text{kg}, \quad \text{gravitational field strength} = 9.8 \, \text{m/s}^2, \quad \text{height} = 4.5 \, \text{m} \] Therefore: \[ \text{GPE} = 3.2 \times 9.8 \times 4.5 = 141.12 \, \text{J} \] Rounding to three significant figures, the gravitational potential energy gained is 141 J.
Reason: The work done on the books when they are carried to the top of the stairs is equal to the gravitational potential energy gained by the books. This is because the work done against gravity is stored as potential energy in the books.
Question 5
Fig. 5.1 shows a tidal turbine. A tidal turbine generates electricity from the energy stored in tides.
(a) State two advantages of using the energy stored in tides for generating electricity compared with using a coal-fired power station. Ignore building and other costs. (Sub-topic – 1.7.3)
▶️Answer/Explanation
Answer:
1. No sulfur dioxide (emission) OR acid rain (produced).
2. No CO2 / greenhouse gases (emitted) OR no / reduces (impact on) global warming.
Explanation:
Tidal energy is a renewable source of energy that does not produce harmful emissions like sulfur dioxide or carbon dioxide, which are major contributors to acid rain and global warming, respectively. This makes it a cleaner alternative to coal-fired power stations.
(b) State two disadvantages of using the energy stored in tides for generating electricity compared with using a coal-fired power station. Ignore building and other costs. (Sub-topic – 1.7.3)
▶️Answer/Explanation
Answer:
1. Suitable locations limited OR locations remote.
2. Marine ecosystems disrupted.
Explanation:
Tidal energy generation is highly location-specific, requiring areas with significant tidal ranges, which are often remote. Additionally, the construction and operation of tidal power plants can disrupt marine ecosystems, affecting aquatic life and habitats.
Question 6
(a) Fig. 6.1 shows a cold drink in a thermal jug. The jug reduces thermal energy transfer from the surroundings to the drink. (Sub-topic – 2.3.1)
State the names of the two processes of thermal energy transfer that are prevented by the vacuum.
Explain how the vacuum prevents these two processes of thermal energy transfer.
▶️Answer/Explanation
Processes: Conduction and convection.
Explanation: A vacuum is an empty space with no particles, so it prevents conduction because there are no particles to transfer energy through collisions. It also prevents convection because there are no particles to move and carry energy from one place to another.
(b) Fig. 6.2 represents a demonstration that shows how water moves when heated. The colour from the crystal shows the flow of the water.
The arrows in Fig. 6.2 show the direction of flow of water in the glass tube when the water is heated. Explain why the water moves in this way. Use your ideas about density. (Sub-topic – 2.3.2)
▶️Answer/Explanation
Explanation: When water is heated, it gains thermal energy, causing the water particles to move faster and spread apart. This makes the heated water less dense than the surrounding cooler water. The less dense, warmer water rises, while the cooler, denser water sinks. This creates a convection current, which is shown by the movement of the coloured water in the glass tube.
Question 7
A student can hear trains passing her house.
(a) Describe the motion that a sound wave gives to air particles. (Sub-topic – 3.4.1)
▶️Answer/Explanation
Sound waves cause air particles to oscillate or vibrate back and forth in the direction of the wave propagation. This motion is longitudinal, meaning the particles move parallel to the direction of the wave.
(b) When the student is at her house, she can hear and see the trains, as shown in Fig. 7.1.
When a train whistle blows, steam comes out of the whistle.
The student measures the time interval between seeing the steam coming out of the whistle and hearing the whistle.
(i) Suggest a suitable device for measuring this time interval. (Sub-topic – 3.4.5)
▶️Answer/Explanation
A stopwatch or a digital timer would be suitable for measuring the time interval between seeing the steam and hearing the whistle.
(ii) The time interval is 1.6 s between the steam coming out of the whistle and the student hearing the whistle.
The speed of sound in air is 340 m/s.
Calculate the distance \( d \) from the whistle to the student. (Sub-topic – 3.4.6)
▶️Answer/Explanation
To calculate the distance \( d \), we use the formula: \[ d = \text{speed} \times \text{time} \] Given: \[ \text{speed of sound} = 340 \, \text{m/s}, \quad \text{time} = 1.6 \, \text{s} \] Therefore: \[ d = 340 \times 1.6 = 544 \, \text{m} \] The distance from the whistle to the student is 544 meters.
(c) State the range of audible frequencies for a healthy human ear. Include the unit. (Sub-topic – 3.4.3)
▶️Answer/Explanation
The range of audible frequencies for a healthy human ear is from 20 Hz to 20,000 Hz (20 kHz).
Question 8
(a) In Fig. 8.1, each diagram illustrates a wave property. (Sub-topic – 3.1)
Draw a line from each diagram to the correct wave property.
▶️Answer/Explanation
Answer:
Top diagram — Diffraction
Bottom diagram — Refraction
(b) An object O is placed in front of a converging lens.
Fig. 8.2 shows two rays of light from the object passing through the lens. (Sub-topic – 3.2.3)
(i) State the name of the line XY in Fig. 8.2.
(ii) State the name of the point labelled F in Fig. 8.2.
(iii) On Fig. 8.2, draw an arrow to represent the image of O.
(iv) Using a ruler, measure the focal length of the converging lens.
(v) Describe characteristics of the image in Fig. 8.2.
Choose words from the list. Tick (✓) three boxes.
▶️Answer/Explanation
Answer:
(i) Principal axis
(ii) Principal focus
(iii) Vertical line from point where rays cross to the principal axis
(iv) 1.9 cm
(v) Enlarged ✓, Inverted ✓, Real ✓
Question 9
Fig. 9.1 shows an electric water heater. The heater is connected to the mains electrical supply.
Fig. 9.2 shows the electrical safety label for the heater. (Sub-topic – 4.4)
(a) (i) Explain why the safety label states, ‘Disconnect from the mains supply before removing the plastic cover.’
(ii) The heater is switched on. Calculate the current in the heater. Use the information in Fig. 9.2.
▶️Answer/Explanation
(i) The safety label states to disconnect from the mains supply before removing the plastic cover to prevent the risk of electric shock or electrocution. The plastic cover acts as an insulator, and removing it while the heater is connected to the mains could expose live electrical components, which could be dangerous if touched.
(ii) To calculate the current in the heater, we use the formula: \[ \text{Current} = \frac{\text{Power}}{\text{Voltage}} \] From Fig. 9.2, the power of the heater is 720 W, and the voltage is 230 V. Therefore: \[ \text{Current} = \frac{720}{230} = 3.13 \, \text{A} \] So, the current in the heater is approximately 3.1 A.
(b) Table 9.1 shows some electrical meter readings for the water heater.
| Date | Meter Reading (kWh) |
|---|---|
| 1st October | 3771 |
| 31st October | 3797 |
Electrical energy costs 18 cents per kWh.
Calculate the cost of using the heater from 1st October until 31st October.
▶️Answer/Explanation
Solution: First, calculate the total energy used by the heater: \[ \text{Energy used} = \text{Final reading} – \text{Initial reading} = 3797 – 3771 = 26 \, \text{kWh} \] Next, calculate the cost of the energy used: \[ \text{Cost} = \text{Energy used} \times \text{Cost per kWh} = 26 \times 18 = 468 \, \text{cents} \] Therefore, the cost of using the heater from 1st October until 31st October is 468 cents.
Question 10
(a) Different materials have differing magnetic properties.
(i) State the name of a material that is suitable for a temporary magnet. (Sub-topic – 4.1.1)
▶️Answer/Explanation
Answer: Soft iron
Explanation: Soft iron is suitable for temporary magnets because it can be easily magnetized and demagnetized. It has low coercivity, meaning it loses its magnetism quickly once the external magnetic field is removed.
(ii) State the name of a material that is suitable for a permanent magnet. (Sub-topic – 4.1.3)
▶️Answer/Explanation
Answer: Steel
Explanation: Steel is suitable for permanent magnets because it retains its magnetism for a long time. It has high coercivity, meaning it resists demagnetization.
(iii) State how a magnet can show that a material is non-magnetic. (Sub-topic – 4.1.4)
▶️Answer/Explanation
Answer: A magnet does not attract a non-magnetic material.
Explanation: Non-magnetic materials, such as plastic or wood, are not attracted to a magnet. If a material does not respond to a magnetic field, it is considered non-magnetic.
(b) A teacher uses the arrangement in Fig. 10.1 to demonstrate an electric bell. When the switch is closed, the hammer repeatedly hits the metal gong. (Sub-topic – 4.5.3)
Using the information in Fig. 10.1, explain why the hammer repeatedly hits the metal gong when the switch is closed.
▶️Answer/Explanation
Answer:
- When the switch is closed, a current flows through the circuit, creating a magnetic effect in the coil.
- The coil and nail become an electromagnet, attracting the springy iron strip.
- As the iron strip is attracted, it moves towards the electromagnet, causing the hammer to hit the gong.
- When the iron strip moves, it breaks the circuit, stopping the current and demagnetizing the coil.
- The springy iron strip then returns to its original position, closing the circuit again, and the process repeats.
Explanation: The electric bell operates on the principle of electromagnetism. When the circuit is closed, the electromagnet attracts the iron strip, causing the hammer to strike the gong. The breaking of the circuit stops the current, allowing the iron strip to return to its original position, and the cycle repeats, causing the hammer to repeatedly hit the gong.
Question 11
Fig. 11.1 represents all the particles in a beryllium atom. (Sub-topic – 5.1.2)
(a) (i) The symbol for the element beryllium is Be. Give the nuclide notation for the isotope shown in Fig. 11.1.
\(_{……}^{……}\textrm{Be}\)
(ii) The key for Fig. 11.1 gives the names of two types of particle. One label is missing.
Complete the key by adding the name of the third type of particle shown in Fig. 11.1.
▶️Answer/Explanation
Answer:
(i) The nuclide notation for the isotope shown in Fig. 11.1 is \( \frac{9}{4}Be \).
(ii) The missing particle in the key is neutrons.
(b) Fig. 11.2 shows four different particle diagrams, A, B, C and D. (Sub-topic – 5.1.2)
(i) State which diagrams show an isotope of beryllium.
(ii) State which diagram shows a positive ion.
▶️Answer/Explanation
Answer:
(i) Diagrams A, B, and D show isotopes of beryllium.
(ii) Diagram A shows a positive ion.
(c) A scientist uses a detector and counter to measure the count rate due to radiation emitted from a radioactive source. (Sub-topic – 5.2.4)
The first measurement is 400 counts/min.
The scientist takes another measurement 6 hours later. This measurement is 50 counts/min.
Calculate the half-life of the radioactive source.
▶️Answer/Explanation
Answer:
The half-life of the radioactive source is 2 hours.
Explanation:
The count rate decreases from 400 counts/min to 50 counts/min in 6 hours. This is a reduction by a factor of 8 (400 → 200 → 100 → 50), which corresponds to 3 half-lives. Therefore, the half-life is \( \frac{6 \text{ hours}}{3} = 2 \text{ hours} \).
Question 12
There are eight planets in our Solar System. Table 12.1 shows the names of some of the planets in order of distance from the Sun. (Sub-topic – 6.1.2)
(a) Complete Table 12.1 by writing the names of the other planets in order of increasing distance from the Sun.
▶️Answer/Explanation
The order of the planets from the Sun is:
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
(b) The planets in Table 12.1 orbit the Sun. State the names of two other types of natural objects that orbit the Sun. (Sub-topic – 6.1.2)
▶️Answer/Explanation
Two other types of natural objects that orbit the Sun are:
- Asteroids
- Comets
(c) Complete the sentences to describe Mercury and Jupiter. Use words from the list. (Sub-topic – 6.1.2)
large rocky gaseous small liquid
Mercury is …… and ……
Jupiter is …… and ……
▶️Answer/Explanation
Mercury is rocky and small.
Jupiter is gaseous and large.