Qstnid -I-10-a Book Is Lifted From The Floor And Is Kept In An Almirah. One Person Says That The Potential Energy Of The Book Is Increased By 20 J And The Other Says It Is Increased By 30 J. Is One Of Them Necessarily Wrong? - 08: Work And Energy

with Solutions -

#10
A book is lifted from the floor and is kept in an almirah. One person says that the potential energy of the book is increased by 20 J and the other says it is increased by 30 J. Is one of them necessarily wrong?
Ans : Yes, one of them is necessarily wrong. We measure potential energy from a reference level chosen by the observer. However, the change in potential energy of a body does not depend on the level of reference.
Page No 130: