Complete the statement. Assume that Bobby's mass did not change.
The gravitational potential energy stored between Bobby and Earth () as he rode the escalator.

 - decreased
 - stayed the same
 - increased
Think about how the distance between Bobby and the center of Earth changed.
The second floor is higher than the first floor. As he rode the escalator toward the second floor, the distance between Bobby and the center of Earth increased. So, the gravitational potential energy stored between Bobby and Earth increased as he rode the escalator.