Question

A body whose true weight is 14 kg appears to weigh 14
kg when weighed with the help of a spring balance in a
moving lift. The acceleration of the lift at the time was

Answer 1

Explanation:

1)

m = mass of the body hanged from spring balance = 15 kg

W = actual weight of the body hanged in downward direction = mg = 15 x 9.8 = 147 N

a = acceleration of the lift in upward direction = 2 m/s²

F = reading of the spring balance

force equation for the motion of the body hanged in the lift is given as

F - W = ma

F - 147 = 15 (2)

F = 177 N

2)

a = acceleration of the lift in downward direction = 2 m/s²

force equation for the motion of the body hanged in the lift is given as

W - F = ma

147 - F = 15 x 2

F = 117 N

3)

Since the lift is going at constant velocity

a = acceleration of the lift = 0 m/s²

W - F = 0

F = W

F = 147 N