Wednesday, November 21, 2012

Momentum and Impulse in Basketball: By Rachel Valdivieso

Elastic Collisions, and Impulse

Sports often contain many real-life physics applications.  This video

shows two basketball players in a collision.

Assuming that player 20’s mass was 90kg and player 13’s mass was 120kg.

Player 20 was traveling in the +x direction at 1.5m/s and collided with player 13

traveling 2.0m/s in the –x direction (-2.0m/s). Assuming the collision was perfectly

elastic, each player’s velocity (with direction) and impulse (with direction after the

collision) can be calculated using the law of conservation of momentum and the

impulse equation. (These calculations refer to the velocity and impulse of each

player before player 20 fell.)The collision is assumed to be elastic.

The law of conservation of momentum equation:

Since momentum is conserved in elastic collisions:

[Equation 1] MAVA+MBVB=MAVA+MBVB  [Equation 2] VA-VB= -VA+VB

The axis of orientation is established and remains constant throughout the problem:

positive velocities move in the (+x direction) to the right and negative velocities

move in the (-x direction) to the left.

MA =90kg
MB =120kg
VB= -2.0m/s


Plugging in the known initial velocities and masses to the momentum equation:


using equation 2 to solve for VB in terms of VA:



solve  for VA:

VA= (-2.5m/s) (-x direction)

With 1 significant figure:

VA -3m/s (-x direction)

Plugging -2.5m/s into equation 2 to solve for VB:

VB=(3.5m/s)+(-2.5m/s)=1 m /s (+x direction)

With 1 significant figure:

VB1m/s (+x direction)

Now that the velocities are known, each player’s impulse can be calculated:

Impulse on player #20:

Impulse=MAVA-MAVA=the change in momentum for player 20

Plug in known values to solve for impulse:

Impulse=(90kg)(-2.5m/s)-(90kg)(1.5m/s)= -360kgŸm/s

With one significant figure and direction, since impulse is a vector:

Impulse -400kgŸm/s (-x direction)

Impulse on player #13:

Impulse=MBVB-MBVB=the change in momentum

Plug in known values to solve for impulse:


With one significant figure and direction, since impulse is a vector:

Impulse≈ 400kgŸm/s (+x direction)

       Assuming the collision is perfectly elastic, momentum is conserved and the

players feel equal magnitudes of impulse in the opposite direction.

1 comment:

  1. Hi

    The Z Code software is live...and after doing a few bets myself and
    pocketing the cash, I can tell you that this is REAL!

    ===> 80% Win Rate? It's Not a BUG? [Proof Inside] <=====

    Grab your copy risk free quickly before they run out... everyone is
    crazy about it and the race is on!

    No wonder... I mean,

    even if you are skeptical you really NEED to check out how transparent
    these guys truly are...
    Videos of bank accounts stuffed with money, videos of bookmaker
    accounts, screenshots proving how effective this killer software is,
    videos of how to make the money risk free, hundreds of real people

    ...proof, proof, and more proof!! All sitting there for you to
    absorb! Don't take my word for it - you have to see it to believe it.

    ===> Z Code Win Bet Software is LIVE! [WITH PROOF! <=====

    Heads up, though - I just got word from the developers that, due to
    all of the traffic they're getting, their servers are working at peak
    performance to keep the website up and running...

    Thankfully they have 2 more that the software runs on .. and plenty of
    backup ones.. but the website is under heavy hits, so they might close
    the doors anytime..

    Do yourself a favor and get your risk-free copy NOW (protected by a 60
    day money-back guarantee)

    ===> Sports Insiders secret ZCode software beats the bookies? <=====

    Hope you make it in time!

    [your closing]

    P.S. There's a free tool, called Sports Predictions, that you can get
    simply by visiting the site...
    They're giving it out as a gift so head over there quickly :)


Note: Only a member of this blog may post a comment.