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Question
A bullet initially moving with a velocity 20 m/s strikes a target and comes to rest after penetrating a distance 10 cm into the target. Calculate the retardation caused by the target.
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Solution
Initial velocity u = 20 m/s
Final velocity v = 0
Distance travelled s = 10 cm = 0.1 m
Let acceleration be 'a'.
Using the third equation of motion,
v2 − u2 = 2as
We get,
(0) 2 − (20) 2 = 2(a) (0.1)
a = −(400/0.2) m/s2
a = −2000 m/s2
Thus, retardation = 2000 m/s2
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