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Calculating Force

  1. Mar 9, 2007 #1
    Sammy Sosa swings at a 0.15kg baseball and accelerates it at a rate of 3.0 x10^4 m/s^2. How much force does Sosa exert on the ball?

    F=ma

    (30000m/s^2)(0.15kg) = 4500 N

    Can someone make sense out of these problems? How is it accelerating at that rate? I've seen car crashing problems not even get that much higher force. Sosa can hit a car and get a home run. LOL
     
  2. jcsd
  3. Mar 9, 2007 #2
    Can anyone explain it? I'm assuming all the problems in the packet come to realistic answers.
     
  4. Mar 9, 2007 #3

    Doc Al

    User Avatar

    Staff: Mentor

    The time of contact of bat with ball is very short--so force and acceleration are high.
    A car has quite a bit more mass than a baseball. (And is not as bouncy.) :wink:
     
  5. Mar 9, 2007 #4
    Here's another problem...

    An ax has a mass of 2.5kg and is swinging at 25m/s.
    A man chops a tree and the ax stops at 2.3cm in the tree.

    (vf^2 - vi^2)/2d = a

    625m/s / 0.046m = 13000m/s^2

    F=ma
    (13000m/s^2)(2.5kg) = 34000 N

    So how is that person so strong? A car can make a much bigger dent to another car than a man can do with a hammer. The force values never make any sense.
     
    Last edited: Mar 9, 2007
  6. Mar 9, 2007 #5

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    You are confusing the transient forces generated by contact dynamics (bat on ball, axe head on wood) with the much smaller forces Soso and the wood chopper use to get the ball/axe moving. Contact dynamics typically generate very high but very short-lived forces.
     
  7. Mar 9, 2007 #6
    A change in momentum results from a force acting over a period of time, and is a product of the force and the time it acts over. A force that large acting over a small period of time is not uncommon
     
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