A crane lifts four pallets of bricks, each of which weigh 5000 N. The crane lifts each pallet a height of 30m. The crane takes 4 minutes to do this.
How much useful power did the crane produce to lift the bricks?

A.150 000 W

B.625 W

C.2500 W

D.37 500 W

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.