Chapter 4.2, Problem 25SSC

To determine

The parts of the ride during which the real and apparent weights be the same.The parts of the ride during which the apparent weight is less than the real weight.The parts of the ride during which the apparent weight is more than the real weight. And to draw free body diagrams.

Explanation of Solution

Introduction:

The weight of an object changes in lift depending upon direction of motion of the lift, this weight is called apparent weight.

The apparent weight and real weight will be same when the lift is going upward or downward with constant velocity.

The below free body diagram shows the case when apparent weight is same as the real weight.

  

Figure-(1)

Apparent weight will be less than the real weight when the lift is going downward with increasing or decreasing speed.

The free body diagram below shows the case when apparent weight is less than the real weight.

  

Figure-(2)

Apparent weight will be more than the real weight if the lift is going upward with increasing or decreasing speed.

The free body diagram below shows the case when apparent weight is greater than the real weight.

  

Figure-(3)

Conclusion:

Therefore, the apparent weigh is same as real weight when the elevator is moving with constant velocity, less when elevator is going downward with variable speed and greater if elevator is going upward with variable velocity the free body diagrams are shown above.