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Goalkeeper

The goalie has the most important job of the game. Because he is tasked with defending the goal to the best of his ability, he has to have a good understanding of momentum, vectors, and impulse. And by crouching low, he is creating potential energy by acting as a spring, allowing his legs more room to accelerate so that he can jump higher.

 The physics of a goal keeper

  A goalkeeper is constantly analyzing the various vectors on the field. He considers the possible angles that the person with the ball might have for a shot, while also keeping track of who they might pass to, and if they have an angle for a shot. He also has to anticipate the Magnus effect on the ball so that he can position accordingly to defend. His goalie gloves were designed to minimize the force imparted on the goalie's hand. Soft foam maximizes impulse by absorbing the momentum of the ball for a little longer, allowing the goal keeper to grab a hold of more of the shots. When attempting to catch the ball, the goalie's hands must be positioned so that the friction is enough to stop the ball from slipping through his hands, without his hands being so open as to allow the ball to deflect rather than being caught. A goal keeper also keeps his weight forward, so that he can jump forward while deflecting the ball. Because of the conservation of momentum, this causes the ball to deflect as far away from the goal as possible. A goalkeeper may also try to redirect the ball by hitting it at an angle. This changes the ball's motion vector. Even if the ball is still moving away from the kicker, it is deflected over the goal rather than into it. The goalie's punch is often less inclined about changing the ball's horizontal speed, and more focused on increasing it's motion in the vertical direction.