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Bounce of football (kinetic and potential energy)

  1. Nov 7, 2009 #1
    1. The problem statement, all variables and given/known data

    A football (european) that hits ortogonally a surface will reflect such that the kinetic energy of the ball after the collision will be a fraction of the kinetic energy of the ball before the collision. The football makes a free fall from 50 cm to a floor and jumps to the height of 40 cm. After that the football is kicked into a wall (of the same material as the floor) from 5 meters. The ball hits the wall ortogonally and lands on the floor in the distance a from the wall. Find a.

    2. Relevant equations

    We assume that 4/5 of the football's energy is conserved in a collision because

    U1 = 4/5*U2
    where U1 is the potential energy before the collision, U2 after.

    3. The attempt at a solution

    The ball will have 4/5 of its energy conserved after the collision with the wall. This will make the ball go 4/5 the distance it was shot from, making it reach 4 m.

    This might be right, but we suspect it's too easy. The fact the Ekin energi has v2 makes me suspect our current suggestion is wrong. a might also depend on how hard the ball is shot, but the excercise doesn't state any force that makes the ball go to and collide with the wall.

    Thanks a lot!! :-)
  2. jcsd
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