A single mass (m 1 = 4.3 kg) hangs from a spring in a motionless elevator. The s

Question

A single mass (m1= 4.3 kg) hangs from a spring in a motionless elevator. The spring constant is k = 259 N/m.

Now, three masses (m1= 4.3 kg, m2= 12.9 kg and m3= 8.6) hang from three identical springs in a motionless elevator. The springs all have the same spring constant given above.

The elevator is moving downward with a velocity of v = -2.5 m/s but accelerating upward at an acceleration of a = 4.5 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.)

What is the magnitude of the force the upper spring exerts on the upper mass?

Explanation / Answer

M a = T - M g        T and a are opposite in direction to g

M = 4.3 + 12.9 + 8.6 = 25.8 kg

The upper spring must support all of the masses

T = 25.8 (9.8 + 4.5) = 369 N

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