Question

Are the objects described here in static equilibrium, dynamic equilibrium, or not in equilibrium at all? ( Explain how the answers are correct )
A) A 200 pound barbell is held over your head. (static equilibrium)
B) A girder is lifted at constant speed by a crane. ( Dynamic equilibrium)
C) A girder is being lowered into place. It is slowing down. (not in equilibrium)
D) A jet plane has reached its cruising speed and altitude. (Dynamic equilibrium)
E) A box in the back of a truck doesn't slide as the truck stops. ( Dynamic equilibrium)

Answer 1