A person stands on a bathroom scale in an elevator and reads a weight of 687.8 N

Question

A person stands on a bathroom scale in an elevator and reads a weight of 687.8 N. What is the acceleration of the elevator if the person's mass is 81.0 kg? Make sure to include the correct sign in your answer, for the direction of the acceleration.

I found the correct answer of -1.31 m/s^2

The same person tries another experiment, using an accelerometer app on a mobile phone during a different elevator ride. The app shows an acceleration of +1.45 m/s2. What is the force exerted by the legs on the person's upper body, assuming that the legs are 32% of the person's mass?

Explanation / Answer

m(g+a) = 687.8

=> 81*(9.8-a) = 687.8

=> a = -1.31 m/sec^2

force = m(g+a) = (68/100)*81*(9.8+1.45) = 619.65 N

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