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Homework Help: How to figure out acceleration in a F=ma problem?

  1. Jan 7, 2012 #1
    1. The problem statement, all variables and given/known data

    Problem for physics project (How morce force does a person use on another's head in a punch, kick etc)

    A 8lb medicine ball (to resemble a human's head weight) will be punched to accelerate X speed.

    2. Relevant equations

    (no clue what equations...)

    d=Vi t + 1/2 at^2

    3. The attempt at a solution

    I want to figure out the force required to do so.
    So F=ma . I have m and i want to get F therefore i should figure out acceleration.

    I have no clue on how to figure out acceleration.(Initial velocity?...)

    I can get time and distance the ball will travel, (its like a half parabola problem)
    Last edited: Jan 7, 2012
  2. jcsd
  3. Jan 7, 2012 #2
    What data will you get directly from your experiment?
  4. Jan 7, 2012 #3
    I can get any data that i know how to get...

    Not sure if Vf = 0

    From the experiment i can gather :

    The distance of the ball to the ground.

    The distance of the ball to the point it lands
    (imaginary line going down to the ground from the ball and measure that way)

    And a stop watch to record the air time then averaging out the data.
  5. Jan 7, 2012 #4
    You'll need to work out how long the ball will take to fall to the ground under the accelleration of gravity.
  6. Jan 7, 2012 #5
    Dosen't quite answer anything... and i can get by with recording that info with a stop watch.(kinda)

    The problem is that i can't figure out velocity without acceleration and acceleration without velocity.

    And i have no idea how to record any of those data.
  7. Jan 7, 2012 #6
    I'm not exactly sure if this would work but if you calculate how long it takes the ball to hit the ground.

    Then measure the horizontal distance travelled.

    Then divide the horizontal distance by the time you calculated.
  8. Jan 7, 2012 #7
    i did an experiment ones that looks lots like this one, but then totally different. We had a bike and wanted to know the deceleration of the bike. We got that one by using a videocamera. The video we putted on a computer with some kind of program (really common, but I can't recall the name, but I guess that you will probably have something similar) on in that was capable of calculating the speed the bike had between each frame. And from that the computer could calculate the acceleration (acceleration is noting more then the speed differentiated). So maybe you can use a similar set-up?

    I hope you could follow me, English is not my mother languish and I find it hard to explain something in it:P

    good luck with your experiment:)
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