A body starts from a point with a velocity and uniform acceleration a. The direction of acceleration is reversed when the velocity of the body becomes 5u. The velocity of body al point will be

Options

A. `-v`
B. `-5v`
C. `-7v`
D. `-9v`

Answer

c

Explanation

Here `v^(2)-u^(2)=2aS` =Constant
`:. (5v)^(2)-v^(2)=v^(2)-(5v)^(2)`
or `v^(2)=49v^(2)` or v=-7v
neglecting+ ve sign