Edexcel GCSE Combined Science: Physics: Conservation of Energy

A country is deciding whether to build a new wind farm or a new gas-fired power station to generate electricity. Wind is a renewable energy resource; natural gas is a non-renewable fossil fuel.

Evaluate the use of wind power compared with a gas-fired power station for generating electricity. In your answer you should refer to reliability, the environment, and the idea of a renewable versus a non-renewable resource. (6 marks)

A diver of mass 60 kg climbs onto a diving board that is 5.0 m above the surface of the water and then dives off, falling towards the water. Take the gravitational field strength $g = 10\ \text{N/kg}$g=10 N/kg.

(a) Calculate the gravitational potential energy stored in the diver at the top of the board, relative to the water surface. Use $E_p = mgh$Ep​=mgh. (2 marks)

(b) Assume that all of this gravitational potential energy is transferred to the kinetic energy store as the diver reaches the water. Using $E_k = \tfrac{1}{2}mv^2$Ek​=21​mv2, calculate the speed of the diver as they reach the water. (2 marks)

A warehouse worker pushes a heavy crate along a level floor. The worker pushes with a steady horizontal force of 150 N and the crate moves 8.0 m in the direction of the force. It takes 12 s to move the crate this distance.

(a) Calculate the work done by the worker on the crate. Use $W = Fd$W=Fd. (2 marks)

(b) Calculate the useful power developed by the worker while moving the crate. Use $P = \dfrac{E}{t}$P=tE​. (1 mark)

An electric motor is used to lift a load. In a test, the motor takes in 800 J of electrical energy. Of this, 600 J is transferred usefully to the gravitational potential energy store of the load, and the rest is dissipated to the surroundings as thermal energy.

(a) Calculate the efficiency of the motor as a percentage. Use $\text{efficiency} = \dfrac{\text{useful energy output}}{\text{total energy input}} \times 100$efficiency=total energy inputuseful energy output​×100. (2 marks)

(b) State how much energy is wasted (dissipated) by the motor, and name the store this wasted energy is transferred to. (1 mark)

A ball of mass 0.50 kg is moving along the ground at a speed of 6.0 m/s.

Calculate the kinetic energy stored in the ball. Use the equation $E_k = \tfrac{1}{2}mv^2$Ek​=21​mv2. Show your working and give the unit. (2 marks)

A solar cell and a coal-fired power station are two ways of generating electricity.

Name one renewable energy resource and one non-renewable energy resource used to generate electricity. (1 mark)