Oscillations

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Question : 8
Total: 25
A spring balance has a scale that reads from 0 to 50 kg. The length of the scale is 20 cm. A body suspended from this balance, when displaced and released, oscillates with a period of 0.6 s. What is the weight of the body?
Solution:  
Here, m = 50 kg,
Maximum extension, y = 20 – 0 = 20 cm = 0.2 m
Maximum force, F = mg = 50 × 9.8 = 490 N
∴ Spring constant,
k=
F
y
=
490
0.2
=
490×10
2
=2450Nm1

When a body of mass M is suspended from the spring balance, it oscillates with a period of 0.6 s.
∵ Time period, T=2π
M
k
or T2=4π2
M
k

M=
T2k
4π2
=
(0.6)2×2450
4×(3.14)2

M = 22.36 kg
∴ Weight of the body,
W = Mg = 22.36 × 9.8 = 219.1 N = 22.36 kgf
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