Problem 31. If you place your physics book on a shelf at a height of Yı above ground level, you give it a potential energy of PE1. If you place

it on a different shelf at y2ground level, its potential energy is PE2 = 2PE1. What is the relationship between y2and y1?above \text { (a) } \quad y_{2}=y_{1} / 2 \text { (b) } \quad y_{2}=\sqrt{2} y_{1} \text { (c) } \quad y_{2}=2 y_{1} \text { (d) } \quad y_{2}=4 y_{1} \text { (e) None of these }