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Homework Help: Urgent Problem

  1. Dec 4, 2004 #1
    Urgent!!! Problem!!!!!

    This is an urgent problem please help!!!!:

    The force exerted on a 0.145-kg baseball by a bat changes from 0.0 N to 1.0x10^4 (^4= 4th power) over 0.0010 seconds, then drops back to zero in the same amount of time. The baseball was going toward the bat at 25 m/s.

    A) Draw a graph of force versus Time. What is the average force exerted on the ball by the bat?
    B) What is the acceleration of the bat?
    C) What is the Final velocity of the ball, assuming that it reverses direction?

    please tell me how to do and the answer
    Last edited: Dec 5, 2004
  2. jcsd
  3. Dec 4, 2004 #2
    What have you done so far?
  4. Dec 4, 2004 #3
    well since the first question asks about the average force i used the formula F=MA to figure out the force and i got for the force 3625N (not sure if its right) i got this by caluclating the acceleration using A=v-v0/ t which gave me A=25000 since V=25 and V0=0, however this is just for the first half i need to do this again except for the backwards part to figure out the average
  5. Dec 4, 2004 #4


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    The first questions asks the average force. They give you the maximum force. It's [tex] 1 * 10^4[/tex]
    Average force should be intuitive. The force starts at 0, rises to maximum, then returns to zero.

    Hint: What's the average of these numbers {0,1,2,3,4} and what's the average of these numbers {4,3,2,1,0}
    I'd do it the same way.
  6. Dec 4, 2004 #5
    would that mean the avg force is 12,500?
  7. Dec 5, 2004 #6
    if u use the gradient formula ...

    m = \frac{y_2 - y_1}{x_2 - x_1}

    then the average will be ...
  8. Dec 5, 2004 #7


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    Gold Member

    no, using the numbers I gave as an example:
    Hint: What's the average of these numbers {0,1,2,3,4} and what's the average of these numbers {4,3,2,1,0}
    the average of 0,1,2,3,4 is 2 because 0+1+2+3+4 = 10 and there's 5 members and 10/5 = 2
    notice that 2 is exactly half of your highest value.
    You could use the formula [tex]average = \frac{|initial - final|}{2}[/tex] which would also give you 2.

    In your problem, the highest value is 1 * 10^4 N.
  9. Dec 5, 2004 #8
    can someone work out the problem and tell me what you get. I got answers but i would like to make sure they are right, and i don't have the data with me i left it at a friends house.
  10. Dec 5, 2004 #9
    Eric..ur a bad bot

    eric this was supposed to be an extra credit assignment.. i am very dissapointed in you. you will be suspended immidietly on monday.

    with love Dr. Lubert
  11. Dec 5, 2004 #10
    very funny Jeff, sorry guys thats my dumb friend Jeff
  12. Dec 5, 2004 #11
    Eric what happened

    eric i was watching u in tefillah and i was very disappointed that you were not davaning properly u will be suspended on monday

    with love: that guy
  13. Dec 5, 2004 #12
    NO!!!!! I am terribly sorry, i did not mean to offend That Guy!!!
    I will daven better in tefilah
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