When a football is initially at rest and a player kicks it, the speed of the football increases from zero as a result of the force applied by the player's foot. This force transfers energy to the ball, causing it to accelerate and gain kinetic energy. Specifically:
- Initially, the football's speed is zero because it is at rest.
- When the player kicks the ball, the foot applies a force over a short contact time, which changes the ball's momentum and increases its speed from zero to a certain value depending on the force and duration of contact.
- The ball's speed increases rapidly during the kick, reaching a velocity that can be quite high (for example, around 21 m/s in some cases), depending on the strength and technique of the kick
- After the foot loses contact with the ball, no further force is applied by the player, so the ball continues moving at the speed it had at the moment of release, gradually slowing down due to external forces like air resistance and gravity
Biomechanically, the speed the ball attains depends on factors such as the velocity of the foot before impact, the player's technique, and the force applied during the kick. Experienced players can generate higher foot velocities, resulting in greater ball speeds
. In summary, the speed of the football starts at zero and increases sharply as the player kicks it, reaching a maximum immediately after the kick, after which the ball moves freely through the air at that speed until other forces act on it
