Suppose you were to drop a 9 lb bowling ball from the top of the Empire State Building, which is about 440 m tall, onto a machine that would catch it and then convert its kinetic energy into electrical energy. For how long could the resulting energy light a 100 W light bulb? Is it actually possible to convert mechanical energy to electrical energy with 100% efficiency?

1 answer

Step 1:

Using equation of motion 3-
v^2 = 2as
v^2 = (2)(10)(440)
= 8800

Step 2:

Kinetic energy = (1/2)mv^2
= (1/2)(4)(8800)
(Because 9 pounds is 4 kgs)
= 17600 J

Step 3:

Kinetic energy = Electical Energy = E = 17600J

E/t = P
t = E/P
t = 17600/100
= 176

Therefore, the time is 176 seconds

______________

No, it is not possible, since the ball meets with air resistance which causes a certain loss of energy, and all electronic equipments have resistance which causes a minor power loss.