A body starts with velocity $u$ and moves on a straight path with constant acceleration. When its velocity becomes $5 u$ the acceleration is reversed in direction without changing the magnitude. When it returns to starting point its velocity becomes:

-u

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-3u

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-7u

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-5u

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Solution

The correct option is A -u
When the body is moving forward,
$(5 u)^{2} - u^{2} = 2 a s$
$\Rightarrow 25 u^{2} - u^{2} = 2 a s$
Similarly, when the direction is reversed, after travelling the same distance
$v^{2} - (5 u)^{2} = - 2 a s$
From the two equations, we get
$v = u$
Since the direction is opposite to the first direction, velocity at the starting point is $- u$

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