An electric chain hoist is used to lift a 250 kg crate.  The motor provides 2.1 kW of input power to the hoist system, which has an efficiency of 86%.  How long will it take to lift the crate to a height of 10.0m?

A heavy box is pulled by a rope on a horizontal surface. (a) Assume that there is no frictional force between the box and the surface. If the tension force in the rope is 240 N and the box moves by the distance of 5.6 m in 2.9 s, what is the power output of the work done by the tension force?  (b) Assume that the surface is rough and there is frictional force between the box and the surface. If the box moves at the constant speed of 0.31 m/s when the tension force is 240 N, what is the power output of the work done by the tension force?

A 2,000-kg pile driver is used to drive a steel I-beam into the ground. The pile driver falls 3.00 m before coming into contact with the top of the beam, and it drives the beam 14.6 cm farther into the ground as it comes to rest. Using energy considerations, calculate the average force the beam exerts on the pile driver while the pile driver is brought to rest.

A 2.2 kg object is initially moving at 5.78 m/s. After a time of 4.9 s, the object is moving at a rate of 8.72 m/s. What net work was done on the object during that time?