How much work is required to lift a 3.06 kg object from the bottom of a 8.5 m de

Question

How much work is required to lift a 3.06 kg object from the bottom of a 8.5 m deep well? In J.

A sled and rider with a combined weight of 69 kg are at rest on the top of a hill 30 m high. (a) What is their total energy at the top of the hill? In J.
(b) Assuming there is no friction, what is the total energy on sliding halfway down the hill? In J.

A man pushes a lawn mower on a level lawn with a force of 214 N. If 44% of this force is directed downward, how much power does he expend in pushing the mower 6.9 m in 20 s? In W.

Explanation / Answer

1 . W = mgh = 3.06 * 9.8 * 8.5 = 254.898 J ;

2 .( a ) P = mgh = 69 * 9.8 * 30 = 20286 J ;

total energy remains the same , = 20286 J ;

3 .

since 44 % is downward ,

56 % is frontward ,

W = 0.56 * 214 * 6.9 = 826.896 J ;

P = W / t = 826.896 / 20 = 41.34 W   <---------------ans

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