Question

A person holding a 30 kg box 1 m above the floor puts it down. How much work was done ? Remember , the force of an objects weight = mass times gravity
A. 0.0j

B. 30j

C. 147 j

D. 294 j

Answer 1

Hey friend! The answer is D. 294 j

Answer 2

As long as the box was 1m off the floor. it's potential energy was m•g•h = 30•9.8 = 294 joules. When the person stopped restraining the box and allowed it to move, gravity did 294 joules of work on the box, and would have done more if the floor hadn't been in the way. The person did no work on the box.