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

Options

A. `136N`
B. `134N`
C. `158N`
D. `68 N`

Answer

A

Explanation

Given mass `=2kg`
`x (t) =pt + qt^(2) + rt^(3)`
`v =(dx)/(dt) = p + 2qt + 3rt^(2)`
`a = (dv)/(dt) = 0 + 2q +6rt` ltbr gtat `t =2s, a =2q + 6 xx 2 xx r`
`= 2q +12r`
`= 2 xx 4 + 12 xx 5`
`= 8 + 60 =68 m//s`
Force ` =F =ma`
`=2 xx 68 =136 N` .