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Horizontal and vertical component of acceleration

  1. Oct 6, 2009 #1
    Honestly, I am soo confused...And this is the last problem left. If I get it wrong then I'm in trouble. Please help! I don't know what to do at all.

    A skier squats low and races down a(n) 11 degrees ski slope. During a 5 second interval, the skier accelerates at 2.3 m/s^2.

    (A) What is the horizontal component of the skier's acceleration (perpendicular to the direction of free fall)? Answer in units of m/s^2.

    (B) What is the vertical component of the skier's acceleration? Answer in units of m/s^2.


    Givens:
    11 degree ski slope, 5 seconds interval, acceleration = 2.3 m/s^2.


    2. Relevant equations:
    No clue what to use :S



    3. The attempt at a solution
    All my previous attempts were completely off topic :(

    Please can someone do this problem, and show me how it's done?
     
  2. jcsd
  3. Oct 6, 2009 #2

    berkeman

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    Staff: Mentor

    No we won't do your problem for you. That's not how the PF works. Please re-read the Rules link at the top of the page

    Draw the free body diagram for the skier and show the forces and acceleration. That should get you to the answer pretty quickly.
     
  4. Oct 6, 2009 #3
    I dont know how to show the forces..The is the only problem thats holding me back.
     
  5. Oct 6, 2009 #4

    berkeman

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    Staff: Mentor

    Have you drawn a free body diagram before? What will it look like in this problem?

    Presumably there is no friction, so there will be no friction force back up the slope. So the only force on the skier is due to what? Draw that force and its vertical and horizontal components. Remember that F=ma, and remember the kinematic equations of motion under constant acceleration. What are those equations for position and velocity?
     
  6. Oct 6, 2009 #5
    I'm still lost because the assignment I'm doing has problems that have not yet been taught by our instructor....I'm still not clear on how to conduct this problem. How do i draw the force with its vertical and horizontal components? I mean the only givens we really have is acceleration, time and the degree of the slope
     
  7. Oct 6, 2009 #6

    berkeman

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    Staff: Mentor

    You're fishing trying to get me to do the work for you. Aint going happen. Post the kinematic equations of motion that you will use. Tell us what forces act on the skier. Do the work.
     
  8. Oct 6, 2009 #7
    You said F=ma.

    Well, how can we use that if we only have acceleration that fits in that? We don't have mass.
    Also, what would we use the 11 degrees for?
     
  9. Oct 6, 2009 #8

    berkeman

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    Staff: Mentor

    Yes, you will use F=ma, where F is the sum of all the vector forces you have in your free body diagram (FBD). The 11 degrees is the slope of the incline, which you will use to resolve your forces into horizontal and vertical components. You will use the kinematic equations of motion to get the accleration from the final speed and distance. Use wikipedia if you need more info on the kinematic equations of motion or FBDs:

    http://en.wikipedia.org/wiki/Free_body_diagram

    I'm off the PF for a while starting now. Please spend the time reading the info at wikipedia, and draw your FBD. I don't believe you when you say this hasn't been covered in class. Even if true, the wikipedia links provide the info.
     
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