1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Static friction question with no mass

  1. Jan 3, 2008 #1
    1. if a car is speeding off on a surface of asphault, no slipping tires, estimate static friction for a drag racer that covers the quarter mile in 6 seconds

    My attempt:

    I made a Free Body Diagram: Weight (W) down wards, Normal force (fn) upwards, and friction static friction to the right (Ffs). ou rteacher set that up for us.
    I then tried calculating acceleration.

    a=18.33 m/s/s i think that answer is completely wrong and then i tried figguring out fn

    Fn-W= ma

    But i think you have to divide the Fn by the mass times gravity

    but i don't have the mass..... so i don'/t know phelp pleasee
  2. jcsd
  3. Jan 3, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    You don't have enough information in the question
    I could have a tractor pulling a sledge do 1/4mi in 6 seconds (with a big enough engine) or a I could have an air hockey puck do the same.

    You need at least the mass and power.
  4. Jan 3, 2008 #3

    Doc Al

    User Avatar

    Staff: Mentor

    coefficient of static friction

    As mgb_phys points out, you don't have enough information to find the friction force. But you can estimate the coefficient of static friction, which might be what your teacher meant.

    Hints: When finding the acceleration, convert .25 miles to meters, not feet. How does the friction force relate to the normal force?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Static friction question with no mass