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!

Acceleration of a ball thrown vertically upwards

  1. Sep 17, 2015 #1
    1. The problem statement, all variables and given/known data
    image.jpg
    I chose A because since the acceleration of the ball is positive vertically upwards, the acceleration downwards is negative, and at the turning point, acceleration is zero.. The correct answer is B. Why?
     
  2. jcsd
  3. Sep 17, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Perhaps you are confusing acceleration (which is the rate of change in velocity) with velocity? Why do you think the acceleration changes? Does the force change?
     
  4. Sep 17, 2015 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Think about this:

    If the acceleration were 0 at the maximum height, the ball would just sit there suspended. Does that happen?

    If the acceleration were positive as the ball rises, then it would get faster and faster as it does. Does that happen?
     
  5. Sep 17, 2015 #4
    Oh..I get what you mean.. I thought acceleration was zero at the maximum height, because v=0.. but I shouldn't see into velocity, it's the change, thanks for the help!
     
  6. Sep 17, 2015 #5
    But why, whenever we do Kinematics questions, where an object falls, we take acceleration as g= + 9.81ms^-2 ?
     
  7. Sep 17, 2015 #6

    Doc Al

    User Avatar

    Staff: Mentor

    I'm not exactly sure what you are asking, so I'll mention two things:
    (1) g is usually taken as a positive constant; g = 9.81ms^-2;
    (2) for a falling body, the acceleration is downward with magnitude g; whether you express that downward acceleration as + or - depends on your sign convention. (Sometimes it's convenient to use "down = positive".)
     
  8. Sep 18, 2015 #7
    Ok thanks !
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Acceleration of a ball thrown vertically upwards
Loading...