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!

Physics: When a 58-g tennis ball is served?

  1. Sep 22, 2009 #1
    1. The problem statement, all variables and given/known data

    When a 58-g tennis ball is served, it accelerates from rest to a speed of 36 m/s. The impact with the racket gives the ball a constant acceleration over a distance of 36 cm. What is the magnitude of the net force acting on the ball?


    2. Relevant equations



    3. The attempt at a solution

    Fnet= ma
    to find a i need time
    so i used v=d/t to find the time. 36=36/t so t=1sec
    now to find a i used V-V_0=at so 36=a*1 so a=36
    now i plugged it in
    Fnet= 58g*36=2088

    what am i doing wrong?
     
  2. jcsd
  3. Sep 22, 2009 #2
    You are very sloppy with your units. Go back through your calculations making sure the units are correct. I can see at least two major place where you units are incorrect. See if this fixes the answer.
     
  4. Sep 22, 2009 #3
    ok so i changed the m=0.058kg, and d=0.36m
    so t=0.01s which makes a=3600m/s2 so fnet= 3600*0.058=208.8. did i do a conversion wrong/
     
  5. Sep 22, 2009 #4
    The speed of the ball isn't 36 m/s during the entire acceleration, but only at the end of it, so you can't use v = d/t and the time you computed is wrong.
    use x = (1/2) a t^2 to find out when the ball has moved 36 cm.
     
  6. Sep 22, 2009 #5
    how can i use x= 1/2 at^2 if i dont know the t or a? what do i use for t? i tried using v^2-V_0^2=2a(x-x_0) but that didnt work out?
     
  7. Sep 22, 2009 #6
    You know x = 0.36m = (1/2)at^2 and v = at = 36 m/s
     
  8. Sep 22, 2009 #7
    oh ok thanks its 104.4
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Physics: When a 58-g tennis ball is served?
Loading...