April 23rd, 2012, 03:45 AM  #1 
Newbie Joined: Apr 2012 Posts: 1 Thanks: 0  Circular Motion Question!
A car is traveling 10 m/sec on a road where friction is 70% of the car's weight. What is its minimun turning radius? This is 10th grade physics, thanks for your help! 
April 23rd, 2012, 05:01 AM  #2 
Member Joined: Mar 2012 Posts: 60 Thanks: 0  Re: Circular Motion Question!
For this problem you can refer to the case of circular motion. The magnitude of the acceleration is therefore a=v^2/r. N II: F=m*a, where no sigma is needed since there is only one force acting in the horizontal plane. So, now you have: 0.7mg=m*a=mv^2/r (negative sign on the lefthandside of the equation since the positive direction points outward for polar coordinates.) In the above expression I have used the fact that the friction force is 70% of the cars weight, mg, along with the fact that it is a good approximation to assume the friction force to be the only force acting in the horizontal plane. The mass must not be zero for the problem to have a physical meaning, so it is safe to divide the expression by m: 0.7g=v^2/r r=v^2/(0.7g) And there is your answer. 

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