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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 ______.
Options
`(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.
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Solution
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.
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