Work, Energy and Power Solved Problems

Work done is the product of the component of the force in the direction of the displacement and the magnitude of the displacement.

Subjects > Physics > Work, Energy and Power

Which problem do you want to solve ?

  1. A person pushes a `10` `kg` cart a distance of `20` `m` by exerting a `60` `N` horizontal force. The frictional resistance force is `50` `N`. How much work is done by each force acting on the cart ? How much Kinetic energy does the cart have at the end of the `20` `m` if it started from rest ?
  2. A weight of `20` `N` rests on a rough inclined plane of gradient `1` in `10`. What work is done in sliding the weight `10 m` up the plane if the frictional force is `4` `N`?
  3. An athlete can jump to a height of `2.12` `m` on the earth. What height could he jump:
    1. on the moon where the gravitational force is one-sixth of that on earth,
    2. on Jupiter where the gravitational force is `2 1/2` times that on earth?
  4. A mass of `1` `kg` is suspended by a light string and swings like a pendulum so that at the top of each swing it is `0.20` `m` above the lowest position. What type of energy does it have:
    1. at the top of a swing
    2. at the bottom of a swing
    What are the values of the energy in each case?
  5. A boy of mass `50` `kg` runs up a flight of steps `4.5` `m` high in `5.0` `s`. What power does he develop?
  6. Explain why you become physically tired when you push against a wall, fail to move it, and therefore do no work on the wall.
  7. Suppose that the Earth revolves around the Sun in a perfectly circular orbit. Does the Sun do any work on the Earth?
  8. Calculate the kinetic energy of a proton traveling at a speed of `2.94 times 10^8` `m`/`s`. Give your answer in both joules and MeV.
  9. In a `100`-person ski lift, a machine raises passengers averaging `667` `N` in weight a height of `152` `m` in `55.0` `s`, at a constant speed. Find the power output of the motor, assuming no frictional losses.
  10. A ball loses `15.0%` of its kinetic energy when it bounces back from a concrete wall. With what speed must you throw it vertically down from a height of `12.4` `m` to have it bounce back to that same height? Ignore air resistance.
  11. Show that the speed `v` reached by a car of mass `m` that is driven with a constant power `P` is given by
    `v = ((3xP)/m)^(1/3)`
    where `x` is the distance travelled from rest.
  12. A swimmer moves through the water at a speed of `0.22` `m`/`s`. The drag force opposing this motion is `110` `N`. How much power is developed by this swimmer?
  13. How much power, in horsepower, must be developed by the engine of a `1600`-kg car moving at `26` `m`/`s` on a level road if the forces of resistance total `720``N`?
  14. A `52.3`-`kg` trunk is pushed `5.95` `m` at constant speed up a `28.0^0` incline by a constant horizontal force. The coefficient of kinetic friction between the trunk and the incline is `0.19`. Calculate the work done by:
    1. the applied force and
    2. the force of gravity

Recommended Lessons

Which problem do you want to solve ?

  1. A person pushes a `10` `kg` cart a distance of `20` `m` by exerting a `60` `N` horizontal force. The frictional resistance force is `50` `N`. How much work is done by each force acting on the cart ? How much Kinetic energy does the cart have at the end of the `20` `m` if it started from rest ?
  2. A weight of `20` `N` rests on a rough inclined plane of gradient `1` in `10`. What work is done in sliding the weight `10 m` up the plane if the frictional force is `4` `N`?
  3. An athlete can jump to a height of `2.12` `m` on the earth. What height could he jump:
    1. on the moon where the gravitational force is one-sixth of that on earth,
    2. on Jupiter where the gravitational force is `2 1/2` times that on earth?
  4. A mass of `1` `kg` is suspended by a light string and swings like a pendulum so that at the top of each swing it is `0.20` `m` above the lowest position. What type of energy does it have:
    1. at the top of a swing
    2. at the bottom of a swing
    What are the values of the energy in each case?
  5. A boy of mass `50` `kg` runs up a flight of steps `4.5` `m` high in `5.0` `s`. What power does he develop?
  6. Explain why you become physically tired when you push against a wall, fail to move it, and therefore do no work on the wall.
  7. Suppose that the Earth revolves around the Sun in a perfectly circular orbit. Does the Sun do any work on the Earth?
  8. Calculate the kinetic energy of a proton traveling at a speed of `2.94 times 10^8` `m`/`s`. Give your answer in both joules and MeV.
  9. In a `100`-person ski lift, a machine raises passengers averaging `667` `N` in weight a height of `152` `m` in `55.0` `s`, at a constant speed. Find the power output of the motor, assuming no frictional losses.
  10. A ball loses `15.0%` of its kinetic energy when it bounces back from a concrete wall. With what speed must you throw it vertically down from a height of `12.4` `m` to have it bounce back to that same height? Ignore air resistance.
  11. Show that the speed `v` reached by a car of mass `m` that is driven with a constant power `P` is given by
    `v = ((3xP)/m)^(1/3)`
    where `x` is the distance travelled from rest.
  12. A swimmer moves through the water at a speed of `0.22` `m`/`s`. The drag force opposing this motion is `110` `N`. How much power is developed by this swimmer?
  13. How much power, in horsepower, must be developed by the engine of a `1600`-kg car moving at `26` `m`/`s` on a level road if the forces of resistance total `720``N`?
  14. A `52.3`-`kg` trunk is pushed `5.95` `m` at constant speed up a `28.0^0` incline by a constant horizontal force. The coefficient of kinetic friction between the trunk and the incline is `0.19`. Calculate the work done by:
    1. the applied force and
    2. the force of gravity

Recommended Lessons