Work Energy And Power Question 152

Question: When a person stands on a weighing balance, workingon the principle of Hooke’s law, it shows a reading of 60 kg after a long time and the spring gets compressed by2.5 cm. If the person jumps on the balance from a height of 10 cm, the maximum reading of the balance will be

Options:

A) 60 kg

B) 120kg

C) 180 kg

D) 240kg

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Answer:

Correct Answer: D

Solution:

[d] initially, 60g=kx=k(2.5) (i) Let x’ be the maximum compression when the person jumps on the balance, then 12kx=60g(x2+10)

12[60g2.5]x2=60g(x+10)

x2=5x+50

x25x250=0

Solving for x’, we get x=10cm if m kg is the reading, then Mg=k(10) (ii)

From Eqs. (i) and (ii), we get m=240kg



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