A body travels a distance of 2 m in 2 seconds and 2.2m next 4 secs. What will be the velocity of the body at the end of `7 th `second from the start ?

Options

A. ` 5 cms^(-1)`
B. ` 10 cm s^(-1)`
C. ` 15 cm s^(-1)`
D. ` 20 cm s^(-1)`

Answer

B

Explanation

`200=uxx2-(1//2) a(2)^(2)`
or `u-a=100` (i)
`200+220=u(2+4)-(1//2) (2+4)^(2)a`
or `u-3a =70` (ii)
Solving Eqs (i) and (ii) we get `a=15 cms^(-2)` and `u=115 cms^(-1)`.
Further, `v=u-at =115-15 xx7 =10 cm s^(-1)`.