What forces are involved when a football player who is running is tackled by another player?
If the two players collide hard, they will both exert enormous forces on one another. The player running toward the right will experience a force to the left and will accelerate toward the left (slowing down). The player running toward the left will experience a force to the right and will accelerate toward the right (slowing down). The forces involved would cause bruises if they weren’t wearing pads. The pads reduce the magnitudes of the forces on their skin by prolonging the accelerations (smaller forces exerted for longer times). If one player simply trips up the other player, then the player who falls will still come to a stop. However, that player will be experiencing most of the stopping force from the ground by way of sliding friction.