A MAN OF MASS 80 KG ENTERS AN ELEVATOR ABOUT TO DESCEND. WHAT PRESSURE DOES HE EXERT ON THE FLOOR:

a.) what it is at rest?

b.)when it descends with an acceleration of 1m/s

c.) when it is brought to a stop with a deceleration of 1m/s

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Let us call the required pressure Normal Force

letter (a)

Normal Force = mg = 80(9.81) = 784.8 N.

This is also true when the elevator is running at constant velocity (zero acceleration). The pressure he exerted on the floor will change when the acceleration of the elevator is not zero.

letter (b)

Weight = 784.8 N downward

Normal Force = 784.8 - 80 = 704.8 N

letter (c)

Weight = 784.8 N downward

Normal Force = 784.8 + 80 = 864.8 N

Conclusion: Exercise may reduce the weight by 10 kg in less than a month. :)