Football exemplifies physics through Newton's three laws of motion. The action displayed on the field involves mass, velocity, acceleration, torque and more. Newton's first law states that an object at rest will stay at rest. An object in motion will stay in motion unless acted upon by an unbalanced force. The heavier the object, the more resistance it can uphold to a force. So a large linebacker is going to be a tough factor in pushing around. Torque and rotational force allows a small defensive player to tackle a bigger running back. The center of a player's mass is the key. If the player is low to the ground, their center of mass is closer to the ground, so their potential torque is small. When they tackle a player who is running, having their center of gravity farther from the ground, it is easier to push the upright player around his own axis of rotation because there is more torque.