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

Homework Help: Work problem help

  1. Oct 16, 2008 #1
    The toy car is sliding with a kinetic energy of 6.4 J when it locks up its tires (obviously, the toy driver slammed on the toy brakes) and slides for 62 cm, while a frictional force of 0.63 N acts against it. What is the kinetic energy (in Joules) of the car after this frictional work is done?

    I am not sure where to even start.
     
  2. jcsd
  3. Oct 16, 2008 #2

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    Work = force * distance. How much energy is lost in braking, how much does it have left.
     
  4. Oct 16, 2008 #3
    Since W=Force * distance then W = .63N * .62m, So W = .3906Nm with = .39 J. Would you then subtract the Jules? which would = 6.01 Joules
     
  5. Oct 16, 2008 #4

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    From conservation of energy you know that ke(start) = ke(end) + energy lost.
    You know the ke at the start, you have found the energy lost - so ke at the end is easy.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook