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if a object is in lift .the object has acceleration "a"when it is going upwards and the apparent weight of the object is 72N.if the lift is moving downwards it has acceleration "2a" and the weight of the object is 36N.what is the mass of the object?

2007-02-15 00:08:29 · 2 answers · asked by Anonymous in Science & Mathematics Physics

2 answers

F'=ma...W=mg....while moving up,apparent weight is F'=mg-ma...ie...72=9.8m+ma...ie,m=72/9.8+a...NOW while moving downwards,F'=mg-ma...so 36=9.8m-2ma..m=36/9.8-2a...so...2=9.8+a/9.8-2a,19.6-4a=9.8+a....so,a=9.8/5....substituting...m=360/58.8=6.12244898...so mass is 6.12244898gm

2007-02-15 00:42:51 · answer #1 · answered by krienztcruxtz 3 · 0 0

Going up:
F=m(g+a)
72=m(10+a)
72=10m+ma......(1)

goin down:
F=m(g-a)
36=m(10-2a)
36=10m-2ma........(2)

(1)-(2):
36=3ma
a=12/m
So,36=10m-2m(12/m)
36m=10m^2- 24m
10m^2-60m=0
m^2-6m=0
m(m-6)=0
m=0 or m=6
so mass is 6kg

2007-02-15 08:50:25 · answer #2 · answered by yan 2 · 0 0

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