Question

A car of mass m starts from rest and acquires a velocity along east `v = vhati (v > 0)` in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is ______.

विकल्प

• `(mv)/2` eastward and is exerted by the car engine.

• `(mv)/2` eastward and is due to the friction on the tyres exerted by the road.

• more than `(mv)/2` eastward exerted due to the engine and overcomes the friction of the road.

• `(mv)/2` exerted by the engine.

Answer 1

A car of mass m starts from rest and acquires a velocity along east `v = vhati (v > 0)` in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is `underline((mv)/2)` eastward and is due to the friction on the tyres exerted by the road.

Explanation:

Given, the mass of the car = m

As the car starts from rest, u = 0

Velocity acquired along east = `vhati`

Duration = t = 2s.

We know that v = u + at

⇒ `vhati = o + a xx 2`

⇒ `s = v/2 hati`

Force, F = ma = `(mv)/2 hati`

Hence, the force acting on the car is `(mv)/2` towards the east. As the external force on the system is only friction hence, the force `(mv)/2` is by friction. Hence, force by the engine is internal force.