1.1. Identify the unit for energy. 

Tick one box. 

$□$ N

$□$ K

$□$ J

1.2. State why work done is equal to energy transferred.

1.3. Fork-lift trucks are used to move crates in warehouses. Fig. 1.1 shows a crate being lifted to high shelf.

Fig. 1.1

The fork-lift truck lifts a crate of 450 N to a shelf that is 3.9 m above the ground.

 Calculate the work done to lift the crate.

 work done = .................................... 

1.4. Extended tier only

The total energy input for the fork-lift truck to lift the crate is 2500 J 

Calculate the efficiency of the fork-lift truck.

 efficiency = ....................................