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Physics · LAWS OF MOTION
हिन्दीA car of mass \( 1200 \text{ kg} \) accelerates uniformly from rest to a velocity of \( 20 \text{ m s}^{-1} \) in \( 10 \text{ s} \) along a straight level road. The net external force propelling the car is provided by:
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Correct answer · Option A
the static friction force exerted by the road on the tires of magnitude \( 2400 \text{ N} \)
Explanation
Acceleration \( a = \frac{20 - 0}{10} = 2 \text{ m s}^{-2} \). Net external force \( F = ma = 1200 \times 2 = 2400 \text{ N} \). Internal engine forces cannot accelerate the car as a whole; the external force responsible is friction from the road.
