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!

Bike wheel and a step

  1. Nov 7, 2006 #1
    The drawing shows a bike wheel resting against a small step whose height is h=0.120m. The weight and radius of the wheel are W = 25.0N and r = 0.340m. A horizontal force F is applied ot eh axle of the weehl. As the magnitude of F increases, there comes a time when the wheel just begins to rise up and loses contact with the ground. What is the magnitude of the force when this happens?

    I do not even know where to start. I tried to think of torques, but Fg acts on the center of the wheel, whose distance is 0 from the radius. I also tried to think of a normal force exerted by the step, but that just got really weird. Finally, I thought about friction from the floor below the step, but it didin't work out as well.

    And the other problem was the force exerted by the horizontal force, which is also 0 from the radius since it acts directly on the axle.

    And as an extention, can I prove that the height of the step must be between 0 and the radius of the wheel?
  2. jcsd
  3. Nov 7, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Here's a hint: When the wheel begins to rise up, about what point is it pivoting? (It's not the center of the wheel.)
  4. Nov 7, 2008 #3
    Glad I found this. I'm doing the exact same problem out of the Cutnell Physics 7th Ed text. I get that there is a pivot point, but what the heck do I do? This problem is wracking my brains. Can anyone suggest what to start with? Once I get a hint I can probably piece it together. Much appreciated, thanks!
  5. Nov 9, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: What torque must the horizontal force overcome?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Bike wheel and a step
  1. Wheel Climbing a Step (Replies: 5)

  2. Spinning Bike Wheel (Replies: 5)

  3. Spinning Bike Wheel (Replies: 25)

  4. Wheel on Step Question (Replies: 1)

  5. Bike wheel question (Replies: 9)