A 1.2 g pebble is stuck in a tread of a .76 -m-diameter automobile tire, held in place by static friction that can be at most 3.6 N. The car starts from rest and gradually accelerates on a straight rode . How fast is the car moving when the pebble flies out of the tire tread?(adsbygoogle = window.adsbygoogle || []).push({});

Alpha= net Torque/moment of Inertia

So net torque is 3.6 * .38= 1.368 N-m. Moment of inertia is .5mr^2 so that's .5 * .0012 * .38 ^2= 8.664 * 10^-5. so 1.368 N-m/ (8.664 kg-m^2)= 15789 rad/s^2. Now I need to find Theta and then use wf^2= wi^2 + 2alpha * theta. Then use v=wr. But how do I find theta when I don't know the distance is has traveled around the circle. Is it 2pi*r? I am having trouble because how do I know how Many times this pebble went around the circle? I can't find theta if I don't know the full distance is traveled around the circle since theta= s/r where s is the distance the particle goes on it's circular path. How do I find theta?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: How fast is the car moving when

**Physics Forums | Science Articles, Homework Help, Discussion**