A 5 kg mass hangs at the end of a cord that is attached to the ceiling of an elevator. Find the tension in the cord if the acceleration of the elevator is 3.0 m/s2 down.

Answer 1

This is a classic elevator problem. The method of solution is to consider the free body diagram.

If we take the positive direction as up, The net force on the mass is

T -mg where T is the tension in the cord. This is equated to ma (Newton's second law) to get

ma = T - mg. so a = T/m - 9.8

T/m = a + 9.8 since a = -3 , T/m = 6.8 , and T = 5 (6.8) = 34 N