According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.

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Solution

The justification given by the student that the two opposite and equal forces cancel each other is totally wrong. This is because forces of action and reaction never acts on one body. There is no question of their cancellation. The truck does not move because the push applied is far less than the force of friction between the truck and the road.

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