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!

Question about acceleration

  1. Jul 11, 2013 #1
    A ball is pushed in empty space away from gravitation/curvature.

    It attains a speed of 1m/s, then 2m/s, then 3m/s, then 4m/s, then 5m/s and then it continues to move at a constant velocity of 5.1m/s till infinity.

    My question is what things decide that the acceleration would stop at 5.1m/s?

    a) force given to ball
    b) shape of the ball
    c) mass of the ball
    d) something else also
  2. jcsd
  3. Jul 11, 2013 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    You should know that "force equals mass times acceleration". That's all you need.
  4. Jul 11, 2013 #3
    why should acceleration stop at all and uniform motion continue after that?

    How does 'acceleration' know when to stop?
  5. Jul 11, 2013 #4
    When there is no net force acting on the object.
  6. Jul 11, 2013 #5
    F=ma when there are a force there is an acceleration. When theres no force, object will move in a constant velocity
  7. Jul 11, 2013 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    In your example, when you let go and stop pushing it.
  8. Jul 11, 2013 #7
    Very similar to taking your foot off the accelerator in a car....stop applying power, that is, stop apply a net net force, and the acceleration ceases.

    A slightly different perspective applies to uniform circular motion: An object moving in a circular motion...say a ball being swung on a string.... is accelerating due to the change of direction of motion. Remove the force by letting go of the string....'acceleration' ceases as the force from the string is removed.
  9. Jul 12, 2013 #8
    But, here the acceleration seems to increase once the ball leaves my hand. Once I throw the ball, it attains a speed of 1m/s, then 2m/s and finally attains a constant speed/velocity of 5.1m/s. Is it because there are no frictional forces in space?
  10. Jul 12, 2013 #9


    User Avatar
    Science Advisor
    Homework Helper

    I doubt it. Please provide more details of that experiment and how the velocity was measured.

    Normally the only way a ball can accelerate (eg get faster) after it's left your hand is if something else acts on it (eg gravity or an elastic band or ??)
  11. Jul 23, 2013 #10
    Acceleration has stopped at 5.1ms-1
  12. Jul 23, 2013 #11
    The acceleration of the ball due to initially applied force.(F=ma). when this force completely converted into acceleration at 5.1m/s . after F=0 and a=0. so velocity is constant due to zero acceleration.
  13. Jul 23, 2013 #12


    User Avatar
    Science Advisor
    Homework Helper

    I think we can forget about this question. The OP hasn't been back to provide the information requested.

    The OP appears to be saying the ball is "in empty space away from gravitation" yet "acceleration seems to increase once the ball leaves my hand".

    There is either an error with the speed data or another force (not gravity) must be accelerating the ball after it leaves the hand.
  14. Jul 23, 2013 #13


    User Avatar
    Science Advisor
    Gold Member

    or he just doesn't understand the rules/formula as explained to him in the earlier posts

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook