Work, energy and the conservation of energyEdexcel A-Level Physics: Flashcards
What these 12 flashcards ask
- How is work done by a force defined?
- What is one joule?
- What is the work done by a force F at angle θ to the displacement s?
- A force acts at right angles to the motion. How much work does it do?
- What is the equation for kinetic energy?
- What happens to the kinetic energy when the speed doubles?
- What is the equation for the change in gravitational potential energy near the Earth's surface?
- State the principle of conservation of energy.
- What is the speed of an object that falls a height h from rest, with no resistive forces?
- What happens to the energy of an object that does work against friction?
- How can you find the average resistive force on a moving object using energy?
- A box moves at constant speed along the floor. Why is the kinetic energy unchanged?
Exam questions on Work, energy and the conservation of energy
- A traveller pulls a suitcase 20 m along a level airport floor using a handle. The handle is held at 30° above the horizontal and the pulling force is a constant 60 N. The suitcase moves at a constant speed.Calculate the frictional force acting on the suitcase.2 marks
- A child releases a toy car of mass 0.30 kg from rest at the top of a straight ramp. The top of the ramp is 0.80 m above the floor. Take g = 9.81 N kg⁻¹.In practice the car reaches the bottom of the ramp at 3.2 m s⁻¹. Calculate the energy transferred to the surroundings as thermal energy.2 marks
- A skier of mass 70 kg starts from rest at the top of a straight slope and skis down to the bottom. The bottom of the slope is 45 m lower than the top and the slope is 280 m long. At the bottom the skier's speed is 22 m s⁻¹. Take g = 9.81 N kg⁻¹.Calculate the gravitational potential energy lost by the skier, the kinetic energy gained, and the energy dissipated as thermal energy.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).