The student’s logic is flawed because it incorrectly applies Newton’s Third Law. While it’s true that the truck pushes back on us with an equal and opposite force, this force acts on the person pushing, not the truck. The truck does not move because the applied force is counteracted by the friction between its tires and the road, which is a force acting on the truck.
Here’s a more detailed explanation:
Newton’s Third Law:
For every action, there’s an equal and opposite reaction. If you push on the truck, the truck pushes back on you.
Forces Acting on the Truck:
When you push the truck, you’re applying a force. However, the truck is also experiencing friction from the road, which opposes the movement.
Why the Truck Doesn’t Move:
The truck won’t move because the force you’re applying is being counteracted by the frictional force. The truck’s mass also plays a role, as more mass means a greater force is needed to overcome inertia and start moving.
Action and Reaction Forces:
The action and reaction forces (you pushing the truck, and the truck pushing back on you) act on different objects. They don’t cancel each other out because they’re acting on different bodies.
Cancellation of Forces:
Forces only cancel each other out if they are acting on the same object.
The Correct Logic:
The truck doesn’t move because the force you apply is not enough to overcome the friction acting on the truck.