1.

A body of mass 2kg travels according to the law x(t) = `pt + qt^(2) + rt^(3)` where , q = `4 ms^(-2)` , p = `3 ms^(-1)` and `r = 5 ms^(-3)`. The force acting on the body at t = 2s isA. 136 NB. 134 NC. 158 ND. 68 N

Answer» Correct Answer - A
(a) Given , mass =2 kg
`x(t)=pt+qt^(2)+rt^(3)`
`v=(dx)/(dt)=p+2qt+3rt^(2)`
`a=(dv)/(dt)=0+2q+6rt`
At` t=2s,a=2q+6xx2xxr=2q+12r`
=`2xx4+12xx5=8+60=68 ms^(-1)`
Force ,` F=ma=2xx68=136N`


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