Bob can throw a 500 g rock with a speed of 30 m/s. He moves his hand forward 1.0 m while doing so.

Question

chupacabraj · Answer

How much work does Bob do on the rock?

agent0smith · Answer

Work done = change in kinetic energy

You're given final speed, and can assume initial speed is zero.

shamim · Answer

Work done=final kinetiç energy-initial kinetic energy

shamim · Answer

Kinetic energy=0.5mv^2

mww · Answer

Technically should use this formula so that you can take into account the movement of your hand.

$$W = Fs = mas = ms \frac{ v-u }{ t }$$
Where s is the distance the force is applied. Assume u = 0 m/s

mww · Answer

actually you aren't given the time here. so looks like the KE formula will need to be used.

agent0smith · Answer

Distance shouldn't matter. It would take less force to accelerate it over a larger distance, and more force to accelerate it over a smaller distance. 

The work done is the same regardless, since the change in KE is the same. It'd just take more power with less time.