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.

AcademicPhysicsNCERTClass 9

Third law of Motion

There is an equal and opposite reaction$(force)$ for every action force. If an object hits another object with force $(F)$, then the second object also gives the same and opposite force$(-F)$ to the first object.

both action and reaction forces are of equal magnitude but opposite in direction.

When we push the truck parked along the roadside, it will probably not move because the road also offers a static force of friction to oppose the motion of the truck in opposite direction. And the amount of friction offered by the surface of the road is only a required amount to move the truck. If we apply force on the truck more than the required static friction force then the truck will start to move. So if the truck does not move when we push the truck this is due to the static force of friction. However, action and reaction forces don't cancel each other.

Updated on 10-Oct-2022 13:22:33