Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A simple car and friction problem

  1. Nov 19, 2011 #1
    Hi! I cannot answer this question:

    The force that accelerates a car along a flat road is the frictional force exerted by the road on the car's tires. Explain why the acceleration can be greater when the wheels do not spin.

    I know that friction is the force that is moving it forward and the answer is about the coefficients of friction, but I can't seem to understand that if the wheels do not spin, the acceleration will be greater because...well, won't the car remain stationary?
  2. jcsd
  3. Nov 19, 2011 #2


    User Avatar

    Staff: Mentor

    What's the difference between the friction that exists when two surfaces are stationary with respect to each other, and when they are sliding against one another.
  4. Nov 19, 2011 #3


    User Avatar
    Homework Helper

    "Spinning the wheels" means you hit the gas pedal so hard that the wheels turn too fast and slip on the road (usually ice). As soon as they start slipping, their grip on the road is reduced.

    When I first started driving, I could not get my mother's car to go up the icy little hill on our street. The wheels spun, but the car did not move forward. I was pressing the gas pedal too hard. My cousin very gently pressed the gas pedal and the car very slowly went up the hill!

    It has something to do with the kinetic versus static coefficients of friction for rubber on ice.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook