Question

A rock of mass 5kg is pushed over the edge of a cliff which is 200m high

1.ignore air resistance and calculate the speed of the rock at the bottom of the cliff. In reality air resistance cannot be ignored. The rock eventually reaches terminal velocity of 30m/s
2.calculate the kinetic energy of the rock at the bottom of the cliff
3.calculate work done by air resistance
4.calculate the average force exerted by air on the rock

Answer 1

ignoring air resistance, vf^2=2gh

2. with a terminal velocity of 30m/s
final KE=1/2 m 30^2

3. work done by fricion= mgh-1/2 m (30^2)

4. average force by air resistance over the entire flight..

avgforce*h= work done by friction

Answer 2

Thanks for number one is the speed 62.61m/s or 2.25m/s???

Answer 3

And on number 5. The force is 37.75 N am I correct?