31. An elevator is descending with uniform acceleration. Tomeasure the

1.	31. An elevator is descending with uniform acceleration. Tomeasure the acceleration, a person in the elevator dropsa coin at the moment the elevator starts. The coin is 6ft above the floor of the elevator at the time it is dropped.The person observes that the coin strikes the floor in 1second. Calculate from these data the acceleration of thèelevator.
Answer» Let acceleration of lift be a. acceleration of ball with respect to the lift = acceleration of ball with respesct to ground - acceleration of the lift Or, aball(lift)= g - a = 9.8 m/s^2 - a = 32 ft./s^2- a[ 9.8m = 32 ft. ] displacement s = 6 ft. time taken t = 1 s. initial velocity u = 0 s = ut + 1/2 at^2 = 01 + 1/2 (32-a)1*1 = 1/2 (32-a) Therefore, 6 = 1/2 (32-a) Hence a = 20 ft./s^2

31. An elevator is descending with uniform acceleration. Tomeasure the acceleration, a person in the elevator dropsa coin at the moment the elevator starts. The coin is 6ft above the floor of the elevator at the time it is dropped.The person observes that the coin strikes the floor in 1second. Calculate from these data the acceleration of thèelevator.

Answer»

Let acceleration of lift be a.

acceleration of ball with respect to the lift = acceleration of ball with respesct to ground - acceleration of the lift

Or, aball(lift)= g - a = 9.8 m/s^2 - a = 32 ft./s^2- a[ 9.8m = 32 ft. ]

displacement s = 6 ft.

time taken t = 1 s.

initial velocity u = 0

s = ut + 1/2 at^2 = 0*1 + 1/2 (32-a)*1*1 = 1/2 (32-a)

Therefore, 6 = 1/2 (32-a)

Hence a = 20 ft./s^2

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