Narmis, whose mass is 62 kg, boards an elevator and measures his apparent weight

Question

Narmis, whose mass is 62 kg, boards an elevator and measures his apparent weight on a scale sitting on the floor of the elevator. On his way up toward his 5th floor room, Narmis is accelerated in the first 0.5 seconds, then maintains constant speed for 3.0 seconds, then finally rapidly slows down to a stop in 0.5 seconds. The velocity-time graph for his 4.0 seconds of motion is shown below. Use the graph to answer the following questions.

(a) What is the reading on the scale during the time period from 0.0 to 0.5 seconds?
N
(b) What is the reading on the scale during the time period from 0.5 to 3.5 seconds?
N
(c) What is the reading on the scale during the time period from 3.5 to 4.0 seconds?
N

Explanation / Answer

accelartion during 0 to 0.5 sec

by kinematics equation

vf = vi + at

so it is like straight line y = mx +c

where m is slope

so in vf = vi + at

a is slope of graph

so accelartion a = 2/0.5 = 4 m/s2

and deaccelartion is same as =4 m/s2

part a

reading on scale = weight of man + ma = (g+a)m=(9.81+4)62=856.22 N

part b

accelartion is zero so

reading on scale = weight of man = 62g =62*9.81=608.22N

part c

reading on scale = (g-a)m = (9.81-4)*62 = 360.22 N

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