Concept explainers
Are the objects described here in static equilibrium, dynamic equilibrium, or not in equilibrium at all?
a. A girder is lifted at constant speed by a crane.
b. A girder is lowered by a crane. It is slowing down.
c. You’re straining to hold a 200 lb barbell over your head.
d. A jet plane has reached its cruising speed and altitude.
e. A rock is falling into the Grand Canyon.
f. A box in the back of a truck doesn’t slide as the truck stops.
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