A body of mass 10 kg is being acted upon by a force `3t^2` and an opposing constant force of 32 N. The initial speed is `10 ms^-1.`The velocity of body after 5 s is

Options

A. `14.5 ms^(-1)`
B. ` 6.5ms ^(-1) `
C. ` 3.5ms ^(-1) `
D. ` 4.5 ms ^(-1) `

Answer

B

Explanation

` F= 3t^(2) -32 a=(F)/(m) =(1)/(10 ) (3t^(2) -32) =0.3t^(2) -3.2`
` a =(dV)/(dt) rArr int _(10 )(V) dV =int _0^(t) (0.3t ^(2) -3.2)dt `
` rArr " "V-10 =0.1 t^(3) -3.2 t " "rArr at t =5 sec , v = 6.5 m//s `