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Henry gets into an elevator on the 50th floor of a building and it begins moving at...

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quietbang | Student, College Freshman | (Level 2) eNoter

Posted September 28, 2013 at 1:36 AM via web

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Henry gets into an elevator on the 50th floor of a building and it begins moving at t=0.00 s. His apparent weight is shown over the next 24.0s. 

What is Henry's mass if his maximum apparent weight within the elevator is 500.0N?

How far has Henry traveled after 24.0s? 

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted September 28, 2013 at 6:53 AM (Answer #1)

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Henry gets into an elevator on the 50th floor of a building and it begins moving at t = 0.00 s. The figure shows his apparent weight over the next 24.0 s.

If Henry's maximum apparent weight is 500 N and the acceleration due to gravity can be taken to be 10 m/s^2, Henry's mass is 500/10 = 50 kg.

The graph shows, Henry's weight and time on the y and x axes respectively. An assumption is made that the elevator is moving down. As the maximum apparent weight is 500, it can be inferred that Henry travels for 4 seconds at 5 m/s^2, for 16 seconds at 2.5 m/s^2 and for 4 seconds at 0.

The distance traveled in 24 s is `(1/2)*5*4^2` + `5*4*16+(1/2)*2.5*16^2` + `(20 + 16*2.5)*4` = 920 m

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