A single mass m1 = 4.8 kg hangs from a spring in a motionless elevator. The spri

Question

A single mass m1 = 4.8 kg hangs from a spring in a motionless elevator. The spring is extended x = 11 cm from its unstretched length.

Now, three masses m1 = 4.8 kg, m2 = 14.4 kg and m3 = 9.6 kg hang from three identical springs in a motionless elevator. The springs all have the same spring constant that you just calculated above.

Now the elevator is moving downward with a velocity of v = -2.8 m/s but accelerating upward with an acceleration of a = 4.9 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.)

1.What is the distance the MIDDLE spring is extended from its unstretched length?

Explanation / Answer

let,

m1=4.8 kg , m2=14.4 kg, m3=9.6 kg

spring extension x'=11cm

use,

F'=K*x'

m1*g=k*x'

4.8*9.8=k*(0.11)

===> spring constant K=427.64 N/m

1)

here,

F=(m2+m3)*(g+a)

k*x=(m2+m3)*(g+a)

427.64*x=(14.4+9.6)*(9.8+4.9)

==> x=0.825 m

or

extension of middile spring is, x=82.5 cm

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