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 conservation

  1. Feb 20, 2006 #1
    3.4kg rock starts at 25 cm on a plane with a 33degree angle. upon reaching the bottom the box slides along the horizontal. friction coeff is
    .19. how far does the box slide on the horizontal before coming to a rest?

    ok i need to use .5MVi2 + MGy1 = .5MVf2 + MGy2 + Ffrd

    first i need to find the velocity of the box as it hits the end of the incline. i also need the length of the incline.

    i have Y1=.025 meters
    Vf=0
    Vi=0
    M=3.4kg
    g=9.8
    theta=33
    fr=.19

    i keep getting 4.3 meters but its wrong
     
  2. jcsd
  3. Feb 20, 2006 #2
    ok i found the distance from top of incline to bottom of incline to be .459meters using laws of triangles. so if friction is acting the velocity is gsin33-.19gcos33 and that equals 3.7758

    v2=2ad
    v2=3.466
    v=1.8618

    ok so we got Vi at the bottom to be 1.861 and the y1 and y2 at the bottom are both zero and the final V is 0. so is it mv2/2=.19d???? and that comes out to 31.01425 meters???no way!!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook