Work Energy and Power - Result Question 25

28. A rubber ball is dropped from a height of 5m on a plane, where the acceleration due to gravity is not shown. On bouncing it rises to 1.8m. The ball loses its velocity on bouncing by a factor of

[1998]

(a) 1625

(b) 25

(c) 35

(d) 925

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Answer:

Correct Answer: 28. (b)

Solution:

  1. (b) According to principle of conservation of energy,

Loss in potential energy = Gain in kinetic energy

mgh=12mv2v=2gh

If h1 and h2 are initial and final heights, then v1=2gh1 and v2=2gh2 Loss in velocity,

Δv=v1v2=2gh12gh2

Fractional loss in velocity,

=Δvv1=2gh12gh22gh1=1h2h1

=11.85=10.36=10.6=0.4=25



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