In one day, a 75-kg mountain climber ascends from the 1500-m level on a vertical cliff to the top at 2400 m. The next day, she descends from the top to the base of the cliff, which is at an elevation of 1350 m. What is her change in gravitational potential energy (a) on the first day and (b) on the second day?

Solution 1E Step 1: Mass of mountain climber m = 75 kg Climber ascends from level y = 1200 m Vertical cliff to the top y1= 2400 m. The next day, she descends from the top to the base of the cliff, which is at an elevation of y =1350 m. Step 2: (a).Change in gravitational potential energy on first day is P.E = mg(y 2 ) 1 2 P.E = (75 kg)(9.8 m/s )(2400 m 1500 m) 5 P.E = 6.62 × 10 J