A 44 kg man stands on a bathroom scale in an elevator. Starting from rest at the

Question

A 44 kg man stands on a bathroom scale in an elevator. Starting from rest at the top floor, the elevator descends, attaining its maximum speed of 1.90 m/s in 1.22 s. It travels with this constant speed for the next 7.80 s. The elevator then slows down for 2.20 s and comes to rest at ground level
.a)What is the acceleration of the man during the first 1.22 s? Answer in units of m/s2 and use the upward direction as positive.
b) How many forces act on the Man during this elevator ride?
c) What does the bathroom scale register in N during the first 1.22 s?
d) What does the bathroom scale register in N during the 7.80 s period?
e) What does the bathroom scale register in N during the 2.20 s period?
Use 10 N/kg for g and the upward direction as positive.

Explanation / Answer

a) v = u + at

-1.90 = 0 + 1.22 x a

a = - 1.56 m/s2

b) normal force due scale surface . and weight force due to gravity.

c) mg - N = ma

N = 44(9.8 - 1.56) = 362.56 N

d) a = 0

N =mg = 44 x9.8 = 431.2 N

e) a = 1.90 / 2.2 =0.864 m/s2

N -mg = ma

N = 44(9.8 + 0.864) =469.2 N

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