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Question: Answered & Verified by Expert
The system is released from rest with both the spring in unstretched positions. Mass of each block is 1 kg and force constant of each spring is 10 N/m.



Extension of horizontal spring in equilibrium is
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Options:
  • A 0.2 m
  • B 0.4 m
  • C 0.6 m
  • D 0.8 m
Solution:
1422 Upvotes Verified Answer
The correct answer is: 0.4 m
In equilibrium F net = 0

T = kx                   ........ (1)

2 T + kx 2 = mg         ........ (2)

Solving these equations, we have

x = 2 mg 5 k = 2 × 1 × 1 0 5 × 1 0 = 0.4 m



Let v be the speed of block placed horizontally, then

1 2 mv 2 + 1 2 m v 2 2 + 1 2 kx 2 + 1 2 k x 2 2 = mg x 2

or     5 8 mv 2 = mgx 2 - 5 8 kx 2

or     v = 8 5 gx 2 - 5 kx 2 8 m

Substituting the values, we have

v = 8 5 1 0 × 0.4 2 - 5 × 1 0 × 0.16 8 × 1

   = 1.26 m/s

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