Question 1(Subtopic Code: 1.2 )
A cyclist is travelling along a straight road. Fig. 1.1 shows the speed–time graph for the cyclist. The graph is divided into four sections labelled P, Q, R and S.
(a) Calculate the distance travelled by the cyclist in section P from time = 0 to time = 100 s.
(b) Describe the motion of the cyclist in each of sections Q, R and S shown in Fig. 1.1.
(c) The cyclist is moving north along the road. Determine the velocity of the cyclist at time = 300 s. Include the unit.
▶️Answer/Explanation
(a) Distance travelled in section P:
The area under the speed-time graph gives the distance travelled. For section P, the graph is a triangle.
Area = 0.5 × base × height = 0.5 × 100 s × 8 m/s = 400 m.
Answer: 400 m
(b) Motion in sections Q, R, and S:
Q: The cyclist is accelerating.
R: The cyclist is moving at a constant speed.
S: The cyclist is decelerating.
(c) Velocity at time = 300 s:
At time = 300 s, the speed is 12 m/s, and the direction is north.
Answer: 12 m/s north
Question 2(Subtopic Code: 1.8, 1.5.2)
Fig. 2.1 shows a concrete beam resting on the ground.
(a) The weight of the concrete beam is 1540 N. Calculate the pressure on the ground due to the concrete beam.
(b) A builder starts to raise one end of the beam. He uses a force of 1030 N at a perpendicular distance of 120 cm from the pivot. Fig. 2.2 shows the arrangement.
Calculate the moment of the 1030 N force about the pivot.
(c) Describe how the builder can use a smaller force to lift the beam.
(d) The builder positions the beam as shown in Fig. 2.3.
State why the beam shown in Fig. 2.3 is less stable than the beam shown in Fig. 2.1.
▶️Answer/Explanation
(a) Pressure on the ground:
Pressure = Force / Area = 1540 N / (160 cm × 12 cm) = 1540 N / 1920 cm² = 0.8 N/cm².
Answer: 0.8 N/cm²
(b) Moment of the 1030 N force:
Moment = Force × Distance = 1030 N × 120 cm = 123600 Ncm.
Answer: 123600 Ncm
(c) Using a smaller force:
The builder can increase the perpendicular distance from the pivot to reduce the force needed.
(d) Stability of the beam:
The beam in Fig. 2.3 is less stable because its center of gravity is higher, making it more prone to tipping over.
Question 3(Subtopic Code: 1.7.3)
Electricity is distributed from wind turbines to homes and industry.
(a) Statements A–F describe the main stages in the transfer of energy from the Sun to electrical energy in a wind turbine generator. The statements A–F are not in the correct order.
A Air moves from regions of high pressure to regions of low pressure.
B The turbine blades turn a generator.
C Energy from the Sun heats the atmosphere unevenly.
D Uneven heating of the atmosphere produces regions of different atmospheric pressure.
E The generator produces electrical energy.
F Moving air turns the turbine blades.
Complete the flow chart to describe how a wind turbine uses energy from the Sun to generate electrical energy.
(b) State two disadvantages, apart from cost, of using wind turbines to produce electrical energy for homes and industry.
▶️Answer/Explanation
(a) Flow chart:
C → D → A → F → B → E
Explanation:
C: Energy from the Sun heats the atmosphere unevenly.
D: Uneven heating of the atmosphere produces regions of different atmospheric pressure.
A: Air moves from regions of high pressure to regions of low pressure.
F: Moving air turns the turbine blades.
B: The turbine blades turn a generator.
E: The generator produces electrical energy.
(b) Disadvantages of wind turbines:
1. Wind turbines require a large area of land.
2. The energy output is intermittent and depends on wind conditions.
Question 4(Subtopic Code: 1.7.2, 1.7.4)
A student uses an electric motor to lift a load. Fig. 4.1 shows the arrangement.
(a) (i) The motor exerts a force of 25 N on the load. It lifts the load a vertical distance of 2.0 m. Calculate the work done by the motor on the load.
(ii) State the useful energy output of the electric motor when it lifts the load 2.0 m.
(iii) The useful energy output of the motor is less than the energy input to the motor. Explain why the useful energy output is less than the energy input.
(b) The student uses the motor to lift a different load. The motor does 80 J of work when it lifts this load. It takes 5.0 s to lift the load. Calculate the power output of the electric motor.
▶️Answer/Explanation
(a) (i) Work done:
Work = Force × Distance = 25 N × 2.0 m = 50 J.
Answer: 50 J
(a) (ii) Useful energy output:
The useful energy output is the same as the work done, which is 50 J.
Answer: 50 J
(a) (iii) Energy loss:
Some energy is lost as heat due to friction and resistance in the motor.
(b) Power output:
Power = Work / Time = 80 J / 5.0 s = 16 W.
Answer: 16 W
Question 5(Subtopic Code: 2.1.2)
Fig. 5.1 represents some particles of a gas in a metal box. The arrows represent the directions of movement of the particles.
(a) Describe how the particles in Fig. 5.1 exert a pressure on the walls of the box.
(b) The number of gas particles in the box increases. The temperature of the gas does not change. State and explain the effect, if any, on the pressure exerted by the gas particles on the walls of the box.
▶️Answer/Explanation
(a) Pressure exerted by gas particles:
Gas particles move randomly and collide with the walls of the box. Each collision exerts a force on the wall. The pressure is the total force exerted by all collisions per unit area.
(b) Effect of increasing the number of gas particles:
If the number of gas particles increases while the temperature remains constant, the pressure will increase. This is because there are more particles colliding with the walls, resulting in a greater force per unit area.
Question 6(Subtopic Code: 3.1)
A student observes waves on the surface of water in a tank. The waves all have the same wavelength.
(a) The student measures the wavelength of the waves by measuring the distance between one peak and the next peak. Describe a more accurate method for determining the wavelength.
(b) The wavelength of the waves is 4.0 cm and their frequency is 6.0 Hz. Calculate the wave speed.
(c) Fig. 6.1 shows water waves in the tank travelling from deep water to shallow water.
State and explain what happens to the waves as they move from deep water to shallow water.
▶️Answer/Explanation
(a) More accurate method for determining wavelength:
The student can measure the distance between multiple peaks (e.g., 5 or 10 wavelengths) and then divide the total distance by the number of wavelengths to get a more accurate average wavelength.
(b) Wave speed:
Wave speed = Frequency × Wavelength = 6.0 Hz × 4.0 cm = 24 cm/s.
Answer: 24 cm/s
(c) Waves moving from deep to shallow water:
The waves undergo refraction. As the waves enter shallow water, their speed decreases, causing the wavelength to decrease. The frequency remains constant.
Question 7(Subtopic Code: 3.2, 3.3)
Fig. 7.1 represents two rays of light striking a thin converging lens. The rays are both parallel to the principal axis.
\( F_2 \) and \( F_1 \) are the focal points of the lens.
(a) On Fig. 7.1, continue the path of each ray beyond the lens as far as the screen.
(b) Visible light is a region of the electromagnetic spectrum. State one region of the electromagnetic spectrum which has waves of longer wavelength than waves of visible light.
(c) Gamma rays are another region of the electromagnetic spectrum.
(i) Describe one use of gamma rays.
(ii) Describe one harmful effect on people of excessive exposure to gamma rays.
▶️Answer/Explanation
(a) Path of rays beyond the lens:
The rays will converge at the focal point \( F_1 \) after passing through the lens.
(b) Region with longer wavelength than visible light:
Infrared waves or radio waves have longer wavelengths than visible light.
Answer: Infrared or radio waves
(c) (i) Use of gamma rays:
Gamma rays are used in medical treatments, such as cancer therapy, to kill cancer cells.
(c) (ii) Harmful effect of gamma rays:
Excessive exposure to gamma rays can cause cell damage or mutations, leading to cancer or radiation sickness.
Question 8(Subtopic Code: 4.1)
Fig. 8.1 shows the magnetic field pattern around two permanent magnets. The magnets are repelling each other.
(a) On Fig. 8.1, label both the poles on each magnet.
(b) Describe how to plot the shape and direction of the magnetic field pattern shown in Fig. 8.1.
▶️Answer/Explanation
(a) Labeling the poles:
The poles on each magnet should be labeled as North (N) and South (S). Since the magnets are repelling each other, like poles (N-N or S-S) must be facing each other.
(b) Plotting the magnetic field pattern:
To plot the magnetic field pattern, use a plotting compass or iron filings. Place the compass near the magnet and mark the direction of the needle. Repeat this process at various points around the magnet to map the field lines. Alternatively, sprinkle iron filings around the magnets and tap the surface to allow the filings to align with the magnetic field lines.
Question 9(Subtopic Code: 4.3)
Fig. 9.1 shows a series circuit. Two of the components in the circuit are labelled.
(a) State the name of two other components in the circuit.
(b) The current in the lamp is 0.40 A. The potential difference (p.d.) across the lamp is 6.0 V. Calculate the power dissipated in the lamp.
(c) Draw on Fig. 9.1 to show a lamp connected in parallel with the lamp in the circuit. Use the correct symbol.
▶️Answer/Explanation
(a) Other components in the circuit:
Two other components could be a switch and an ammeter.
(b) Power dissipated in the lamp:
Power = Current × Voltage = 0.40 A × 6.0 V = 2.4 W.
Answer: 2.4 W
(c) Lamp connected in parallel:
Draw another lamp symbol connected in parallel with the existing lamp in the circuit.
Question 10(Subtopic Code: 4.5.1)
(a) Fig. 10.1 shows an arrangement used to demonstrate electromagnetic induction.
(i) When the magnet moves towards the coil of wire, the pointer on the sensitive voltmeter deflects to the right. Explain why the pointer deflects.
(ii) State two changes that increase the deflection on the sensitive voltmeter.
(b) Fig. 10.2 shows the symbol for a transformer. The primary coil is connected to a voltage of 180 V a.c.
Calculate the secondary voltage \( V_s \) for the transformer.
▶️Answer/Explanation
(a) (i) Pointer deflection:
The pointer deflects because the movement of the magnet induces an electromotive force (e.m.f.) in the coil, causing a current to flow through the voltmeter.
(a) (ii) Increasing the deflection:
1. Increase the speed of the magnet.
2. Increase the number of turns in the coil.
(b) Secondary voltage \( V_s \):
Using the transformer equation: \( V_s / V_p = N_s / N_p \), where \( V_p = 180 \) V, \( N_p = 4800 \), and \( N_s = 200 \).
\( V_s = (200 / 4800) × 180 = 7.5 \) V.
Answer: 7.5 V
Question 11(Subtopic Code: 5.2)
Fig. 11.1 represents all the particles in an atom which is a radioactive isotope of carbon.
(a) Table 11.1 gives information about the particles shown in Fig. 11.1. Using the information in Fig. 11.1, write in the empty boxes to complete Table 11.1.
(b) A museum displays an item made of ancient wood. When the wood was new, the item contained 8.00 mg of the isotope shown in Fig. 11.1. The item now contains 2.00 mg of the isotope. The half-life of the isotope is 5700 years. Calculate the age of the wood in the item.
▶️Answer/Explanation
(a) Completing Table 11.1:
Electron: 6 particles, orbiting outside the nucleus, charge = -1.
Neutron: 8 particles, in the nucleus, charge = 0.
Proton: 6 particles, in the nucleus, charge = +1.
(b) Age of the wood:
The isotope has decayed from 8.00 mg to 2.00 mg, which is two half-lives (8.00 mg → 4.00 mg → 2.00 mg).
Age = 2 × 5700 years = 11400 years.
Answer: 11400 years
Question 12(Subtopic Code: 6.1)
(a) Fig. 12.1 represents the Earth and the Sun at one point in the Earth’s orbit of the Sun.
Explain the apparent daily motion of the Sun across the sky.
(b) List the four planets closest to the Sun in order of their distance from the Sun.
(c) The Sun mostly consists of two elements. State the two elements.
(d) The Sun is a star in a galaxy. State the name of the galaxy.
▶️Answer/Explanation
(a) Apparent daily motion of the Sun:
The apparent daily motion of the Sun across the sky is due to the Earth’s rotation on its axis. The Earth completes one full rotation every 24 hours, causing the Sun to appear to move from east to west.
(b) Four planets closest to the Sun:
1. Mercury
2. Venus
3. Earth
4. Mars
(c) Elements in the Sun:
The Sun is mostly composed of hydrogen and helium.
(d) Name of the galaxy:
The Sun is part of the Milky Way galaxy.