Rolling Objects With Slipping Question

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The discussion focuses on the dynamics of a ball with a nonuniform mass distribution as it transitions from sliding to rolling without slipping. Participants express confusion about how to approach the problem, particularly regarding the role of friction in providing angular acceleration. It is suggested to define kinetic friction as "F" and to derive equations for linear acceleration (a) and angular acceleration (α), noting that friction ultimately cancels out in the calculations. An alternative method proposed involves analyzing angular momentum about a point on the floor, emphasizing that friction does not influence this analysis. The conversation highlights the complexities of rotational motion and the need for a clear understanding of the underlying physics principles.
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Consider a ball of radius r and total mass m, with a nonuniform but radially symmetric mass distribution inside it, so that it can have an almost arbitrary moment of inertia I. (a) If this ball is projected across a floor with an initial velocity v, and is at first purely sliding across the floor, what is its final velocity when it is rolling without slipping. (b) What is the total energy of the ball?

Equations:
T = I * α
v = r * w
a = r *α
rotational-kinematics formulas

I do not know how to even begin. For the ball to start rolling without slipping, v must equal rw, which means rw must increase. There is no mention of force of friction that might provide the angular acceleration in this problem, so I am quite lost.
 
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Hi Axxaaa! Welcome to PF! :smile:
Axxaaa said:
There is no mention of force of friction that might provide the angular acceleration in this problem, so I am quite lost.

Call the kinetic friction "F", and write out the equations for a and α …

you should find that F cancels out in the end. :wink:

Show us what you get. :smile:
 
Another approach is to consider the angular momentum about a point on the floor. Since friction acts along the floor it will not affect that.
 
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