Student question: A few questions in the homework refer to a point in which objects move without slippage. I know this means that it is rolling, but I don't know what equations need to be satisfied for this to occur.
Dr. Winters' response: Things slide when there is no friction. Things move without slippage when there is friction. So if a problem says that an object moves or rolls without slipping then it means that you need to consider the force due to friction. And you need to consider the force of friction when you are looking at torques, because the force of friction acts on the outside surface of a wheel or ball, and that is a distance r from the center of mass (so there is torque τ=rF (the angle between friction, which acts tangent to the surface, and the radius r is 90 degrees so sinθ=1). It is probably a torque problem.
Hope that helps. Good luck.
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2 comments:
How would you find the minimum coefficient of friction to have no slipping?
Matt, if you're referring to #16, I simply summed up the forces in the horizontal direction and set Ff=(mu)mg.
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