In soccer, the length of the ball in air when it is kicked is the hang time. Air resistance or adding a curve to the ball will increase its hang time. Hang time can be calculated by H= 1/2 g(gravitational acceleration)times t(time) times 1/2. As the player kicks the ball with the inside of his foot he creates a curve on the ball and increases hang time due to air resistance acting on it. Kicking the ball straight will have a low hang time and just keep it low to the ground. The higher the ball is kicked with a curve the more unpredictable it is for the goalie since he might think the ball will go over or he might over jump and miss the ball. When goalkeeping the goalie will either predict where the ball will go if its hit with too great of power or jump quickly to the direction it is going, but this is a risk since the ball might be going too quick for him to react. The greater the force that is used on the goalie legs to jump, the larger the dive to save the ball. The goalie's reflexes help determine his jump speed to see how quickly he dives for the ball. However, the goalie can't predict or react quickly to every shot. The knuckle shot is highly unpredictable in its movement, which leads to a low accuracy rating when used. Goalies are often unable to track and stop an accurate knuckle shot due to its fluctuating movements. This shot has a medium hang time while a finesse shot leads to a higher accuracy, but slower speeds and higher hang time. To do the knuckle shot a person has to kick the ball in a straight line this action will keep the rotation of a soccer ball to a minimum. The more force that is added to the ball the more difficult it is for the goalie to react. This force can be in a straight line or in a curve which cause the goalie to misjudge the movement of the ball.