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!

A simple physics problem which is bothersome -- bowling ball skidding then rolling...

  1. May 10, 2015 #1
    My question is the following. A ball is initially skidding and eventually starts rolling on a flat plane with friction, and later comes to a halt. Which direction does friction act? (see diagram)

    If friction acts to the right, then the translational speed will go up, and that's not right.

    If friction acts to the left, then the angular speed goes up, and that's not right as well.

    Am I missing something? It seems too simple and I feel like a fool to have to ask this.
     

    Attached Files:

  2. jcsd
  3. May 10, 2015 #2

    berkeman

    User Avatar

    Staff: Mentor

    If the ball is thrown to the right, and skids and then slowly starts to spin up, it is because the friction is acting to the left on the bottom of the ball. That slows the translation to the right, and spins up the angular speed of the ball in the clockwise direction.
     
  4. May 10, 2015 #3
    But then if the angular speed is going up, how can the ball reach static equilibrium
     
  5. May 10, 2015 #4

    berkeman

    User Avatar

    Staff: Mentor

    Just like at a bowling alley -- the equilibrium is the ball rolling down the alley floor with some angular velocity and with a translational velocity that is less than it had when first thrown. Losses due to friction is one reason the linear velocity is slower, but there is also the energy that is transferred into the angular momentum of the ball as it spins up. Are you familiar with the Moment of Inertia (MOI) concept yet?
     
  6. May 10, 2015 #5
    Yea, I am... Ah, I see, but I still have a problem, if the angular momentum is increasing, how does the ball stop? Does it stop decreasing, and when? I understand that angular momentum increases in the beginning
     
  7. May 10, 2015 #6

    berkeman

    User Avatar

    Staff: Mentor

    It is mainly rolling resistance (and air resistance) that will slowly bring the ball to a stop. If it's rolling on carpet, then the rolling resistance is high, so it stops sooner. If the rolling resistance is low (like on hardwood flooring), then the ball is going to roll a *long* way...:smile:
     
  8. May 10, 2015 #7

    rcgldr

    User Avatar
    Homework Helper

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




Similar Discussions: A simple physics problem which is bothersome -- bowling ball skidding then rolling...
  1. Rolling ball (Replies: 7)

Loading...