Pearson Edexcel International GCSE
Physics — Topic 4 Paper 3
Energy resources and energy transfers · specification 4.1–4.17
Time allowed: 30 minutes
Total marks: 25
Candidate name:
Centre / class:
Answer all questions. You may use a calculator. Show your working. Take $g=10\,\text{N/kg}$.
1
An electric motor is supplied with $800\,\text{J}$ of energy. $600\,\text{J}$ is transferred usefully to the kinetic store of a flywheel. $200\,\text{J}$ is wasted as thermal energy.
(a) Calculate the efficiency of the motor.
[2]
(b) State the principle of conservation of energy and use it to show that the figures on the Sankey diagram add up correctly.
[2]
(c) Name the pathway that transfers energy to the motor and the store that increases because of the wasted $200\,\text{J}$.
[2]
(Total for Question 1 = 6 marks)
2
A roller-coaster car and passengers have a combined mass of $80\,\text{kg}$. The car is released from rest at a height of $12\,\text{m}$. At the bottom of the first drop the kinetic energy is $7200\,\text{J}$.
(a) Calculate the gravitational potential energy store at the top.
[2]
(b) Calculate the work done against friction on the way down.
[2]
(c) Calculate the speed of the car at the bottom.
[3]
(Total for Question 2 = 7 marks)
3
A house has cavity walls filled with foam and double-glazed windows.
(a) Explain how cavity-wall foam reduces the rate of thermal energy transfer through the wall.
[3]
(b) Explain how double glazing reduces thermal energy transfer through the window.
[3]
(Total for Question 3 = 6 marks)
4
A teacher demonstrates convection using a large beaker of water, a crystal of potassium permanganate and a small Bunsen flame. A heater in a tank of water could be used instead.
(a) Describe a method to show a convection current. State what you would see.
[4]
(b) Explain, in terms of density, why the coloured water moves as it does. State one safety precaution.
[2]
(Total for Question 4 = 6 marks)
END OF PAPER 3