Rolling and Slipping

  • Thread starter 1st2fall
  • Start date
  • #1
1st2fall
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Homework Statement


"A 0.18-kg billiard ball whose radius is 2.8 cm is given a sharp blow by a cue stick. The applied force is horizontal and the line of action of the force passes through the center of the ball. The speed of the ball just after the blow is 3.9 m/s and the coefficient of kinetic friction between the ball and the billiard table is 0.64."
How long does the ball slide before it begins to roll without slipping?
How far does it slide?
What is its speed once it begins rolling without slipping?

Homework Equations


translational kinetic=(1/2)mv^2 Rotational kinetic = (1/2)Iω^2
(when rotating without slipping) v=rω a=rα
Force of friction = force normal * coefficient of friction
Iα=r x F
L= r x p = rmvsin θ (i'm not sure if that is useful yet)

The Attempt at a Solution


I know that it's losing kinetic energy to friction
Force of friction*distance to point where it begins rotating
so I know that after that amount of energy loss... v=rω a=rα will hold true
but I don't know what to do with this...

The net force should just be the force of friction right? so a= Ff/m
so vf=vi+at

I'm confused as to what to do with any of this... it seems like I'm missing something...

I have (1/2)mVi^2=Ff*Δx+.7mVf^2 (added rotational and kinetic assuming that it is rotating)
and that's about all I can do I rearranged somethings and got about .7 seconds for the time. . . but I'm pretty sure that is wrong...

direction please?
 

Answers and Replies

  • #2
1st2fall
22
0
Hope you don't mind me bumping it (I'll compensate by adding some more ideas I have...I'm still working on it and failing haha)
I was thinking about the point of contact...when it begins to roll without slippage, the velocity at that point is 0 right? but with slipping...the sum of the vectors is NOT 0...it's v translation+r(omega) right? could I just use the angular acceleration I have to fine when r(omega) = v?
 
  • #3
1st2fall
22
0
I solved my own problem =DDDD sorry guys...I'm stupid... maybe next time when it's really hard you guys will be interested enough to help? haha
 

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