A car of mass m starts from rest and acquires a velocity along east `upsilon = upsilonhati (upsilon gt 0)` in two seconds Assuming the car moves with unifrom acceleration the force exerted on the car is .

Options

A. `(mv)/(2)` eastward and is exerted by the car engine
B. `(mv)/(2)` eastward and is due to the friction on the tyres exerted by the road
C. more than `(mv)/(2)` eastward exerted due to the engine and overcomes the friction of the road
D. `(mv)/(2)` exerted by the engine

Answer

B

Explanation

Given, mass of the car = m
As car starts from rest, `u=0`
Velocity acquired along east `=v_(i)`
Duration `=t=2s`
We known that, `v=u+at implies v hat(i)=0+a xx 2`
`implies a=v/2 hat(i)`
Force, `F=ma =(mv)/2 hat(i)`
Hence, force acting on the car is `(mv)/2` towards east.
As external force on the system is only driction hence, the force `(mv)/2` is by friction. Hence, force by engine is internal force.