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: Energy err

  1. Aug 12, 2005 #1
    Truck brakes can fail if they get too hot. In some mountainous areas, ramps of loose gravel are constructed to stop runaway trucks that have lost their brakes. The combination of a slight upward slope and a large coefficient of friction in the gravel brings the truck safely to a halt. Suppose a gravel ramp slopes upward at 6 deg. and the coefficient of friction is 0.40.

    Use work and energy to find the length of a ramp that will stop a 15,000 kg truck that enters the ramp at 35m/s

    Delta(kinetic energy)=W(net)

    W(friction)= -u_k*m*g*d(distance)
    W(gravity)= -m*g*(delta y)

    0.5*m*v^2= W(friction) and then you solve for d.. is this right? because i got some really weird answers
  2. jcsd
  3. Aug 12, 2005 #2
    Find y in terms of d using trig and then do W(Friction) + W(gravity) = KE
  4. Aug 12, 2005 #3
    maybe i screwed up the math..because that didnt work


    and that was still wrong, and i cant see where i messed up in the math
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook