## Essential University Physics: Volume 1 (3rd Edition)

a) 0 J b) $49,000J$ c) $-60,000 J$
We know the following equation: $U = mgh$ Knowing that each floor is 3.5 meters tall, we find: a) 0 J; Since she defines her office as ground level, potential energy here is 0 Joules. b) She is 26 floors above her office, so she is $26 \times 3.5 = 91 m$ above her office. Thus: $U= 55 \times 9.81 \times 91 = 49,000J$ c) She is 32 floors below her office, so she is $32 \times 3.5 = 112 m$ below her office. Thus: $U= 55 \times 9.81 \times --12 = -60,000 J$