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Homework Help: Need help on Newton's Law Question and Determining speed

  1. Jan 25, 2017 #1
    <Mentor's note: moved from a technical forum, therefore no template>

    My teacher made this question:

    Iceman is sliding down a 10.0 x 10^(-8) nm ice that is inclined at 20.0 degrees with respect to the horizontal. Iceman is initially at rest. The coefficient of kinetic friction between iceman's feet and the ice is 0.100. Determine Iceman's speed at the bottom of the ice slide.

    What I know:
    1)There are 3 forces as he slides down this slide: force gravity going straight down, force normal which is parallel to the slide @ 20.0 degrees, and force friction which is in the opposite direction he slides down.
    2)The slide is 1m.
    3)ΣFnet= m ⋅ anet .... I then attempted to split it into x and y accordingly where ΣFnetx = m ⋅ anetx &
    ΣFnety = m ⋅ anety
    4) Force friction is equal to -(μ)Fn
    5)Fnety= Fgy + Fn
  2. jcsd
  3. Jan 25, 2017 #2
    Welcome to Physics Forums.
    If you have not done so already, you should draw a free body diagram. And I would recommend drawing your +x axis in the direction of the downward slope of the incline, with your y axis perpendicular to that. By doing that, you will only have an x component of acceleration, which should simplify the problem. Then the y force components will sum to zero, allowing you to find the normal force, which will allow you to find the friction force.

    Seems very strange that the incline length is specified to be 10.0 x 10^(-8) nm. By the way, it looks like it should be +8.
    Also, it was probably just misstated but the normal force is perpendicular to the slide, not parallel.
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