Total marks: 80 · Duration: 75 minutes · Tier: Extended
Instructions to candidates
- Answer all questions.
- Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
- Write your answers in the spaces provided.
- You may use a calculator.
- In calculations, show your working and give the unit of your answer.
- Where a question describes a graph, circuit or apparatus in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 80.
- The number of marks for each question or part question is shown in brackets.
- This paper covers the Core and Supplement content of the Cambridge IGCSE Physics (0625) syllabus.
- Take the acceleration of free fall g = 9.8 m/s².
Paper
Question 1 — Motion (8 marks)
A cyclist starts from rest and accelerates uniformly to 6.0 m/s in 4.0 s. She then travels at a constant 6.0 m/s for 10 s. Finally she decelerates uniformly and comes to rest in 3.0 s.
(a) Calculate her acceleration during the first 4.0 s. [2 marks]
(b) Use the area under the speed–time graph of the journey to calculate the total distance travelled. [3 marks]
(c) Calculate her average speed for the whole journey. [1 mark]
(d) A skydiver falls from a stationary balloon. Explain why the skydiver eventually reaches a constant (terminal) velocity. [2 marks]
Question 2 — Momentum and impulse (8 marks)
(a) Define impulse. [1 mark]
(b) A tennis ball of mass 0.058 kg travels towards a racket at 20 m/s. It leaves the racket in the opposite direction at 30 m/s. The ball is in contact with the racket for 0.0050 s.
(i) Calculate the change in momentum of the ball. [2 marks]
(ii) Calculate the average force exerted on the ball by the racket. [2 marks]
(c) Two ice skaters stand still, facing each other, and then push apart. Skater A has a mass of 60 kg and moves away at 1.5 m/s. Skater B has a mass of 45 kg.
Calculate the speed of skater B. [2 marks]
(d) Explain why the total momentum of the two skaters after they push apart is zero. [1 mark]
Question 3 — Work, power and energy resources (8 marks)
(a) An electric motor raises a lift of mass 650 kg through a height of 24 m in 30 s.
(i) Calculate the gravitational potential energy gained by the lift. [2 marks]
(ii) Calculate the useful power output of the motor. [1 mark]
(iii) The electrical power input to the motor is 8.0 kW. Calculate the efficiency of the motor. [2 marks]
(b) Describe how the energy used in a hydroelectric power station originally comes from the Sun. [3 marks]
Question 4 — Pressure and the kinetic particle model (8 marks)
(a) Calculate the pressure due to the water at the bottom of a lake 12 m deep. The density of water is 1000 kg/m³. [2 marks]
(b) A gas syringe contains 80 cm³ of air at a pressure of 1.0 × 10⁵ Pa. The air is compressed slowly to 32 cm³ at constant temperature. Calculate the new pressure. [2 marks]
(c) Explain, in terms of particles, how a gas exerts a pressure on the walls of its container. [2 marks]
(d) Explain why the pressure of a gas in a sealed, rigid container increases when its temperature increases. [2 marks]
Question 5 — Thermal physics (8 marks)
(a) A 2.4 kW electric kettle heats 1.2 kg of water from 20 °C to 100 °C. The specific heat capacity of water is 4200 J/(kg °C).
(i) Calculate the energy needed. [2 marks]
(ii) Calculate the time this takes, assuming no energy is lost to the surroundings. [1 mark]
(b) The kettle is left switched on for a further 60 s while the water boils. The specific latent heat of vaporisation of water is 2.26 × 10⁶ J/kg. Calculate the mass of water turned into steam. [2 marks]
(c) Explain, in terms of molecules, why evaporation cools the remaining liquid. [2 marks]
(d) Explain why the heating element of a kettle is placed at the bottom. [1 mark]
Question 6 — Light (9 marks)
The refractive index of a type of glass is 1.5.
(a) (i) Calculate the critical angle for light travelling from this glass into air. [2 marks]
(ii) Inside the glass, a ray of light strikes the glass–air boundary at an angle of incidence of 50°. State and explain what happens to the ray. [2 marks]
(b) A ray of light in air strikes the surface of the glass at an angle of incidence of 35°. Calculate the angle of refraction. [2 marks]
(c) An object is placed 25 cm from a converging lens of focal length 10 cm. State three characteristics of the image formed. [2 marks]
(d) Give one use of total internal reflection. [1 mark]
Question 7 — Sound and the electromagnetic spectrum (7 marks)
(a) A student stands 85 m from a tall wall and claps. The echo is heard 0.50 s after the clap. Calculate the speed of sound in air. [2 marks]
(b) (i) What is ultrasound? [1 mark]
(ii) Give one use of ultrasound. [1 mark]
(c) Name the region of the electromagnetic spectrum used for:
(i) mobile phones and wireless internet [1 mark]
(ii) detecting security marks on banknotes. [1 mark]
(d) The speed of electromagnetic waves in a vacuum is 3.0 × 10⁸ m/s. Calculate the wavelength of a radio wave with a frequency of 100 MHz. [1 mark]
Question 8 — Electric circuits (9 marks)
(a) Wire A is 1.0 m long and has a resistance of 4.0 Ω. Wire B is made of the same metal. It is 2.0 m long and has half the cross-sectional area of wire A. Calculate the resistance of wire B. [2 marks]
(b) A 12 V battery is connected in series with a 2.0 Ω resistor and a parallel combination of a 6.0 Ω resistor and a 3.0 Ω resistor.
(i) Calculate the combined resistance of the two resistors in parallel. [2 marks]
(ii) Calculate the current from the battery. [1 mark]
(iii) Calculate the current in the 6.0 Ω resistor. [2 marks]
(c) A potential divider is made from a thermistor in series with a fixed resistor. The output voltage is taken across the fixed resistor. Explain what happens to the output voltage when the temperature rises. [2 marks]
Question 9 — Electromagnetic effects (8 marks)
(a) A magnet is pushed into a coil of wire connected to a sensitive ammeter. The ammeter needle deflects.
(i) Explain why a current is produced. [2 marks]
(ii) State one way of making the needle deflect in the opposite direction. [1 mark]
(b) A transformer has 1200 turns on its primary coil. It changes a 240 V supply into a 12 V output.
(i) Calculate the number of turns on the secondary coil. [2 marks]
(ii) The current in the secondary coil is 2.0 A. The transformer is 100% efficient. Calculate the current in the primary coil. [2 marks]
(c) Explain why electrical energy is transmitted over long distances at a very high voltage. [1 mark]
Question 10 — Nuclear and space physics (7 marks)
(a) Radon-222 (proton number 86) decays by emitting an alpha particle to form an isotope of polonium (Po). Write the nuclear equation for this decay. [2 marks]
(b) The corrected count rate from a radioactive sample falls from 960 counts/min to 120 counts/min in 15 days. Calculate the half-life of the sample. [2 marks]
(c) The Hubble constant H₀ is 2.2 × 10⁻¹⁸ per second. A galaxy is 4.0 × 10²⁴ m from the Earth. Calculate the speed at which the galaxy is moving away from the Earth. [2 marks]
(d) Use the value of H₀ to estimate the age of the Universe in seconds. [1 mark]