A body of mass 2 kg travels according to the law x (t) = `pt + qt^(2) + rt^(3)` where, `q = 4m s^(-2) , p - 3m s^(-1)` and r = `5m s^(-3)`. The force acting on the body at t = 2s is

Options

A. 136 n
B. 134 n
C. 158 n
D. 68 n

Answer

A

Explanation

135 B N
m=2 kg q= 4 `m//s^(2) , p-3 m//s ,r = 5 ms^(3)`
`3t + 4t^(2) + 5t^(3)`
`a= (dx )/(dt ) = 3 (1) + (2t) + 5(3t^(2))`
at t =2
a= 8 + 30(2)
Force F = ma
`= 2xx 68`
`136 N`