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.

The student correctly mentions Newton’s third law, which states that for every action, there is an equal and opposite reaction. However, the conclusion that the forces cancel each other out, resulting in no motion of the truck, needs further explanation.

The equal and opposite forces between the person and the truck do not directly determine whether the truck moves. While the person exerts a force on the truck, the truck exerts an equal force back on the person due to Newton’s third law. However, the truck’s lack of movement is primarily due to the force of static friction between the tires and the road.

If the force applied by the person isn’t greater than the maximum static friction holding the truck in place, the truck will not move. The equilibrium of forces doesn’t imply the cancellation of forces, but rather a balance where there’s no net force to cause the truck’s motion. Hence, the truck remains stationary despite the equal and opposite forces between the person and the truck.