Explain how energy transfers and transformations in mechanical systems always result in some heat loss to the environment, so that the amount of useable energy is reduced.

A motor in an electric hoist lifts a 45 kg crate through a vertical height of 3.2 m in 4.5 s. The electrical energy supplied to the motor during this time is 2,150 J. Explain how energy transfers and transformations in this system result in a reduction of useable energy, and justify why the electrical energy input exceeds the minimum energy required to lift the crate.

A student investigates energy transformations in a toy car powered by a wound spring. The spring stores 2.40 J of elastic potential energy when fully wound. After release, the car travels 3.5 m along a horizontal track and reaches a maximum speed of 0.85 m/s. The car has a mass of 150 g. Explain how energy transfers in this system result in a reduction of useable energy.

A student investigates the efficiency of a mechanical pulley system by measuring the input work (lifting effort) and output work (load raised). The data collected is shown in the table below. Explain how the data supports the conclusion that energy transformations in this mechanical system result in heat loss to the environment, reducing the amount of useable energy.