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Applied Mechanics - Engineering

Q1:

A body of weight 14 g appears to weight 13 g when weighed by a spring balance in a moving lift. The acceleration of the lift at that moment was

A 0.5 m/sec2

B 0.7 m/sec2

C 1 m/sec2

D 1 cm/sec2.

ANS:B - 0.7 m/sec2

T = m1a+mg
In an initial case when mass is it\'s original form such as 14g then there was no acceleration i.e a=o.
So, T=0+mg or T=.0014*9.8 = 0.1372 kgm/sec^2.
Now in the second case when there is downward acceleration. The mass appears to be 13g
So, T=m2a+m2g.

Putting values = .1372=.0013(a)+.0013*9.81.
Solving for a.= a=0.75m/sec^2.