Question

An elevator suspended by a vertical cable is moving downward at a constant speed. The tension in the cable must be A) greater than the weight of the elevator. B) less than the weight of the elevator. C) equal to the weight of the elevator.

Answer 1

(C) because the elevator is not accelerating

Note F = M a = M g (the resultant force on the elevator is due to gravity)

or Fup = Fc the force exerted on the elevator by the cable

and Fdown = Fe the force exerted on the elevator by gravity

F = M a = Fup - Fdown = zero resultant force on elevator