Question

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

Answer 1

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