All flashcards topics

Work, energy and conservation of energyEdexcel International A Level Physics: Flashcards

What these 13 flashcards ask

  • Write the equation for work done by a force.
  • Write the equation for work done by a force at an angle θ to the motion.
  • Define the joule.
  • Why does a force at right angles to the motion do no work?
  • Write the equation for kinetic energy.
  • What happens to kinetic energy if the speed doubles?
  • Write the equation for the change in gravitational potential energy near the Earth's surface.
  • State the principle of conservation of energy.
  • A ball falls from rest through height h with no resistive forces. What is its speed?
  • What does work done against friction equal?
  • A 12 kg sledge is pulled 8.0 m by 50 N at 30° above the horizontal. What work does the pull do?
  • What is the kinetic energy of a 0.15 kg ball at 14 m s⁻¹?
  • Why is energy described as dissipated rather than lost?

Exam questions on Work, energy and conservation of energy

  1. A student pulls a sledge of mass 12 kg along level ground with a rope. The tension in the rope is 50 N and the rope makes an angle of 30° above the horizontal. The sledge moves 8.0 m from rest. A constant frictional force of 30 N opposes the motion.
    Calculate the speed of the sledge after it has moved 8.0 m.2 marks
  2. A ball of mass 0.15 kg is thrown vertically upwards from ground level with an initial speed of 14 m s⁻¹. In a first model, air resistance is ignored. The acceleration of free fall is 9.81 m s⁻².
    In practice the ball reaches a maximum height of only 9.0 m. Calculate the energy dissipated by air resistance as the ball rises.2 marks
  3. A child of mass 30 kg slides from rest down a straight playground slide of length 4.0 m. The top of the slide is 2.5 m above the bottom. The child reaches the bottom at a speed of 5.0 m s⁻¹.
    Calculate the energy dissipated as the child slides down the slide.3 marks
See the full worksheet

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).