1. Not finding help here? Sign up for a free 30min 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!

Question on a problem

  1. Oct 30, 2003 #1

    Le

    User Avatar

    Hi,
    Would you please help me with this problem.
    A batter hits a baseball 1.2 meters above the ground (the point of impact). The ball has mass m = .14g
    Speed V(initital) before the ball hit the bat is 40 meters/sec. The bat does 70 Joules of work on the ball in hitting it. Find the speed of the ball after the ball leaves the bat. The ball reaches a height of 25 meters above the point of impact.
    Thank you,
    Le
     
  2. jcsd
  3. Nov 1, 2003 #2
    In which direction? Down, I presume? And also, I assume that air resistance is negligible.

    From the data given, I just need the mass of the baseball, the gravitational acceleration, and the height it reached. Then, just use the Conservation of Energy. The part before the ball being whacked by the bat is not important at all.
     
  4. Nov 1, 2003 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    [/quote]The part before the ball being whacked by the bat is not important at all.[/quote]

    Yes, it is. The problem says " The bat does 70 Joules of work on the ball in hitting it." and so ADDS 70 Joules to the kinetic energy the ball already had. You use the speed of the ball before the hitting the bat to find its kinetic energy then and add 70 Joules.
     
  5. Nov 2, 2003 #4
    Isn't acceleration due to gravity 9.8ms^2?

    And he says that the mass is .14kg and the height reached is 25m + 1.2m
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Question on a problem
Loading...