1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Heading a Soccer Ball

  1. Aug 29, 2011 #1
    1. The problem statement, all variables and given/known data
    When a soccer ball is kicked toward a player and the player deflects the ball by “heading” it, the acceleration of the head during the collision can be significant. Figure 2-31 gives the measured acceleration a(t) of a soccer player's head for a bare head and a helmeted head, starting from rest. At time t = 7.0 ms, what is the difference in the speed acquired by the bare head and the speed acquired by the helmeted head?
    *i attached the problem and graph

    2. Relevant equations
    Would you just find the area and subtract?

    3. The attempt at a solution
    I attempted to find the area of the collision with the bare head (.75m/s) and the area with the helmeted head (.26m/s) then subtracted to get .49m/s, but the answer at the back of the book says .56m/s. i haven't had calculus yet, so i'm still trying to understand integrals, any advice would be great!

    Attached Files:

  2. jcsd
  3. Aug 29, 2011 #2


    User Avatar
    Homework Helper
    Gold Member

    Hello ang359,

    Welcome to physics forums!
    Try the above again. I think something went wrong.
    That part sounds good to me.
    You're doing fine. You're on the right track. A (definite) integral is "the area under the curve." And that's what you're doing. :smile:

    [Edit: misinterpreted the graph myself (by a factor of 10) in my original post. Made corrections above.]
    Last edited: Aug 29, 2011
  4. Aug 29, 2011 #3


    User Avatar
    Homework Helper

    The only error I see is you have mis-calculated the "area ... with the bare head"

    Not sure how you did it, but with shapes defined by a series of straight line segments like these I just "count the squares" - or in this case rectangles - then convert

    from the scales [ignoring units] you can find that each rectangle represents 20
    The area under the "helmeted head" totals 13 squares so 260 units. Now considering the scales involved - m/s^2 and milliseconds that easily yields your 0.26 m/s.
  5. Aug 31, 2011 #4
    Okay thanks!! i'm not quite sure what i did wrong with the area of the bare head but i'll try it again. it's good to know that i'm somewhat on the right track
  6. Aug 31, 2011 #5
    yeah that makes sense, i'll try the calculations again to see if i made a silly mistake. thanks so much!!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook