A 70.0 kg person stands on a scale in an elevator. (a) What does the scale read

Question

A 70.0 kg person stands on a scale in an elevator.

(a) What does the scale read (in N and in kg)when the elevator is at rest?
_____________ kg
_____________ N

(b) What does it read (in N and in kg) when the elevator is climbing at a constant speed of 2.0 m/s?
_____________ kg
_____________ N

(c) What does it read (in N and in kg) when the elevator is descending at 2.0 m/s?
_____________ kg
_____________ N

(d) What does it read (in N and in kg) when the elevator is accelerating upward at 2.0 m/s2?
_____________ kg
_____________ N

(e) What does it read (in N and in kg) when the elevator is accelerating downward at 2.0 m/s2?
_____________ kg
_____________N

Explanation / Answer

We know that 1 N is equal to 0.101971621 kilogram.

(a) If elevator at rest the normal force acting in upward direction is equal to weight

                     N =mg =(70kg)(9.8m/s2) =686N

                                                            =69.95kg

(b) if he is climbing with Constant speed means no acceleration, so N=70kg*9.8m/s^2=686N and 69.95kg
(c) If he is decending with a constant speed. so it remains the same. i.e 686N and 69.95kg

(d) The elevator is accelerating upward at 2 m/s 2 , Normal component in upwards weigth in downward direction he feels more weight so,

F = ma = N - mg
             N = m(g +a)
                = 70kg(9.80m/s

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