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Lesson: Mechanical Energy Problems

Worksheet: Mechanical Energy Problems • 6 Questions

Q1:

A crate of mass 50 kg is being pushed across a rough surface at a steady 8.0 m/s. The crate is then released and comes to a stop in 10 seconds. What is the average rate at which the frictional force on the crate removes kinetic energy from it?

Q2:

A boy pulls a 5.00-kg cart with a 20.0-N force at an angle of above the horizontal for a length of time. Over this time, the cart moves a distance of 12.0 m on the horizontal floor.

Find the work done on the cart by the boy.

What will be the work done by the boy if he pulled with the same force horizontally instead of at an angle of above the horizontal over the same distance?

Q3:

A boy throws a ball of mass 0.25 kg vertically upward with an initial speed of 20 m/s. The ball moves vertically upward, comes instantaneously to rest, and then accelerates vertically downward and returns to the point from which it was thrown. When the ball returns to its original position, its speed is 17 m/s. How much work was done by air resistance on the ball during its flight?

Q4:

A baseball of mass 0.25 kg is hit at the home plate with a speed of 40 m/s. The baseball lands in a seat in the left-field bleachers, a 120-m-horizontal distance and 20-m-vertically upward distance from the home plate. The baseball has a speed of 30 m/s when it lands. How much work is done on the ball by air resistance?

Q5:

A hockey puck of mass 0.17 kg is shot across a rough floor where the roughness varies at different locations. The variation in roughness of the floor can be described by a position-dependent coefficient of kinetic friction between the puck and the floor. For a puck moving along the -axis, the coefficient of kinetic friction is given by , where is in m.

Find the work done by frictional force on the hockey puck between and .

Find the work done by frictional force on the hockey puck between and .

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