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

TEST TOMMOROW (i was absent when problems were explained)

  1. Dec 21, 2006 #1
    1. The problem statement, all variables and given/known data
    Okay i was absent for 2 days and missed how to do this stuff. And i got a test tommorow. So its not HW i just got to figure out how to do these problems. So i would really appreciate it if someone just did them and explained how. Cause i don't have much time to figure this out myself.

    #1 In a circus performance, a monkey is strapped to a sled and both are given an initial speed of 4.00 m/s up a 20.0º incline track. The combined mass of the monkey and sled is 20.0 kg, and the coefficient of kinetic friction between the sled and incline is .200. How far up the incline do the monkey and sled move?

    #2 A skier starts from rest at the top of a hill that is inclined at 10.5º with the horizontal. The hillside is 200.0 m long, and the coefficient of friction between snow and skis is .0750. At the bottom of the hill, the snow is level and the coefficient of friction is unchanged. How far does the skier move along the horizontal portion of the snow before coming to rest?

    2. Relevant equations

    (sigma)work = 1/2mf^2 - 1/2mvi^2

    3. The attempt at a solution

    I really don't know how to do these so please help me. Thank you so much to anyone that helps.
  2. jcsd
  3. Dec 21, 2006 #2
    1. conservation of energy. The kinetic energy the monkey has at the start needs to be enough to do the work against gravity and friction.

    2. again conservation of energy.

    I'll give you a couple of equations to help you out:


    P.E=mgz (z=change in height)


    Good luck!
  4. Dec 21, 2006 #3
    for number 3 what is wrong with this approach:

    x(196 N 36.9 N - 67.1 N) = 1/2(20 kg)(4 m/s^2)^2

    x comes out to = 1.73 m

    When the teacher told us it was 1.54 m

    any idea?
  5. Dec 21, 2006 #4
    uhhh... I only see two problems
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook