Question

I need answers for #5 and #7

2) m m2 ma Now, three masses (m, = 4.4 kg, m2 = 13.2 kg and mz = 8.8) hang from three identical springs in a motionless elevator. The springs all have the same spring constant given above. What is the magnitude of the force the bottom spring exerts on the lower mass? 86.24 N Submit + 3) What is the distance the middle spring is stretched from its equilibrium length? 79.85 cm Submit 4) Now the elevator is moving downward with a velocity of v = -2.8 m/s but accelerating upward at an acceleration of a = 4.9 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? 388.08 N Submit 5) What is the distance the lower spring is extended from its unstretched length? cm Submit +

Answer 1

from part 3)

spring constant of each spring, k = (m2 + m3)*g/x

= (13.2 + 8.8)*9.8/0.7985

= 270 N/m

5) Extension of the lower string, x = m3*(g + a)/k

= 8.8*(9.8 + 4.9)/270

= 0.4791 m

= 47.91 cm <<<<<<<<<-------------Answer

7) According to Newton's second law,
magnitude of net force on the middle mass, Fnet = m2*|a|

= 13.2*1.8

= 23.76 N <<<<<<<<<-------------Answer