Posted by james on Wednesday, July 25, 2012 at 6:33pm.
A shoe case weighing 40 lb is located on a scale inside a moving elevator that is going upward with the speed of 8 m/s. At time T1 elevator slows down with the acceleration of 3 m/s2 until the time T2. What are the the readings of the scale at T2 and T1 respectively?

science  drwls, Wednesday, July 25, 2012 at 7:54pm
While the upward velocity is decreasing, there is downward acceleration at rate a = 3 m/s^2
At time T1, the scale reads force F.
W  F = M a
F = W  M a = W  (W/g) a
= W (1  a/g) = 40 lb * (6.8/9.8)
If acceleration = 0 at T2, the scale reads 40 lb then. We are able to use metric units for a and g because We are calculating a ratio.
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