Calculate the potential energy of a 20 kg object at rest on a ledge 30 meters above the ground. O 600 J
O 6.5 J
O 50 J
O 9000 J
5886 J

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)

Metals are good conductors of electricity because they

2. which of the following does not affect the electrical resistance of a body? a. material composing the body b. bodies directly surrounding the body c. length of the body > d. temperature of the body