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!

Is there lag as force is converted into acceleration?

  1. Jan 6, 2012 #1
    Sorry for the confusing title, I'm new to physics and have been studying some classical mechanics and I have some conceptual confusion.

    Say someone hits a baseball with a bat. The instant the ball and the bat make contact the ball has zero velocity, and then begins to accelerate as the swing of the bat knocks it forward. Does the entirety of this acceleration occur for the fraction of a second that the ball and bat are in physical contact? So that top speed is reached as soon as the ball and bat are no longer in contact, and from there the ball begins to decelerate due to wind resistance.

    Or does the ball continue to accelerate for some amount of time even after it's no longer in contact with the bat?

  2. jcsd
  3. Jan 6, 2012 #2


    Staff: Mentor

    end contact ends force of bat. Microscopically though you could imagine that the ball is repelling away the bat just a fraction of a fraction of a second pushed by electrons e-field of both ball and bat until the e-field repelling is effectively zero.

    also when you hit a ball the ball deforms and the bat bends a bit and as they separate they go back to their shape. this means that even though the bat has stopped the ball may still be in contact for a fraction of a second and then its free. the instant the bat stops its not accelerating the ball. There could even be some drag if the ball kinda stuck to the bat. Nobody goes to this depth in solving this as these effects all cancel out.

    but we use the ideal case, bat hits ball and accelerates it for a certain distance and then stops. ball is now in free fall going forward but being pulled down by gravity and slowed by wind resistance.
  4. Jan 6, 2012 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, as soon as the ball is no longer in contact with the bat and the force is removed there is no more acceleration.
  5. Jan 6, 2012 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    I believe this is pretty much the definition of "contact". The atoms in the ball never "merge" with the bat, but are repelled away from them. Once the ball has reached a far enough distance they no longer feel any significant force and we can say that the two objects are no longer in contact.
  6. Jan 7, 2012 #5
    Excellent that's what I was hoping was correct, thanks everyone =].
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook