Physics

The correct statement is A: The striking foot pushes backward against the ground. The friction with the ground provides an equal and opposite force forward.

When a runner starts to run, the foot that strikes the ground pushes backward against the ground. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. The action is the force exerted by the foot on the ground in the backward direction.The reaction is the frictional force exerted by the ground on the foot in the forward direction. This frictional force is what provides the net force necessary to accelerate the runner's body forward.

Option B

While the swinging of the leg can help with the running motion and balance, it does not directly provide the propulsive force that accelerates the body forward. The main force for ...