Question

In one day, a 85 kg mountain climber ascends from the 1440 m level on a vertical cliff to the top at 2360 m . The next day, she descends from the top to the base of the cliff, which is at an elevation of 1310 m .
a) What is her gravitational potential energy on the first day? If you choose the reference level for zero potential energy at:
a. the top of the cliff.
b. 1440 m level.
c. 1310 m level.
b) What is her change in gravitational potential energy on the first day?
c) What is her change in gravitational potential energy on the second day?

Answer 1

m g (H - Ho) where mg = 85*9.81 = 834 N

first day
If Ho = 2360
U at start = 834 (1440-2360)
U at top = 834 (2360-2360) = 0
If Ho = 1440
U at start = 834 (1440-1440) = 0
U at top = 834 (2360 - 1440)
If Ho = 1310
U at start = 834 (1440 - 1310)
U at top = 834 (2360 - 1310)

b) U at top - U at start
834(2360 - 1440)

c) U at end - U at top
834 (1310 - 2360)