You push a heavy car by hand. The car, in turn, pushes back with an opposite but equal force on you. Doesn’t this mean that the forces cancel one another, making acceleration impossible? Why or why not?
Solution 21E From the Newton’s third law we know that the action and reaction acts on different object. So, even though, the action and reaction are equal and opposite, they don’t cancel each other. In this problem I am applying force to the car. This is the action which is acting on the car. Now car is also applying same force to me, this is reaction, but acting on me. Since one force is acting on car and the other force is acting on me, they don’t cancel each other. For heavy car, we don’t see the car is moving because of the friction. Frictional force opposes the motion and friction increases with the mass of the object. Hence if we can apply force, which is greater than the friction between the car and the ground, then we can make the car moving.