Question

An 8.0-kg history textbook is placed on a 1.25-m high desk. How large is the gravitational potential energy of the textbook-earth system relative to the desktop?

Answer 1

relative to the floor it is m g h but relative to the desktop it is zero. You can do no work moving it down to the desk top if it is already on the desk top.

Answer 2

98 J
8.0 x 9.8 x 1.25

Answer 3

Wah ha ha ha ha ha

Answer 4

98 j

Answer 5

gravitational potential energy (J) = mass(kg) . gravity (N/kg) . height (m),
GPE = mgh 98J

Answer 6

980 J