Given mass of man is 60kg and reading of weighing machine is 90kg,what is the acceleration of lift in upward and downward direction?
Asked by m.nilu
18th July 2018,
5:03 PM
Answered by Expert
Answer:
Forces acting on Man is shown in figure.
Upward force FMS is the force acting on man and W is the downward force due to gravity (which is his real weight).
We have, FMS - W = m×a or FMS = m×a + W = m×(g+a) ;
when acceleration of lift in upward:- we have a = (FMS/m) - g = [ (90×9.8)/60 ] - 9.8 = 0.5×9.8 = 4.9 m/s2
when acceleration of lift in downward:- we have FMS = m×(g-a)
hence when lift accelerated upward machine reading is more than man's true weight.
When lift accelerated downward machine reading is less than his true weight.
But in this question only one weight machine reading, i.e, 90 kg is given ,
which can be taken as reading for upward motion.
so we can not workout this question for downward motion
Answered by Expert
27th July 2018,
1:07 PM
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