1) Pushing on a car will not always change the car's mechanical energy, but it does change yours since your physically using most of your energy to push the car.
2) In order for a cars kinetic energy to increase, the car has to be in motion when it is going down a hill, because when you go down hills and objects like that; you tend to increase in kinetic energy.
Answer:
5.90 ft/s^2
Explanation:
There are mixed units in this question....convert everything to miles or feet
and hr to s
28 mi / hr = 41.066 ft/s
Displacement = vo t + 1/2 at^2
599 = 41.066 (8.9) + 1/2 a (8.9^2)
solve for a = ~ 5.90 ft/s^2
Let us list out what we know from the question.
Initial Velocity
since the piton is 'dropped'.
Vertical Displacement of the piton D = 215 m
Acceleration due to gravity 
Final Velocity 
Using the equation,
and plugging in the known values, we get

Simplifying by taking square-root on both sides gives us 
Thus, the speed of the piton just before striking the ground is 65 m/s.