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: Physics problem help

  1. Oct 9, 2011 #1
    1. The problem statement, all variables and given/known data

    The problem is in the attachment.

    2. Relevant equations

    3. The attempt at a solution

    I didn't know how to answer this after trying many times. Please tell how to answer this question. How to approach it, please.

    MASS IS 7.1 NOT 7.6.

    Attached Files:

    Last edited: Oct 9, 2011
  2. jcsd
  3. Oct 9, 2011 #2


    User Avatar
    Gold Member

    You have a graph of velocity vs time.
    Can you find the acceleration of the box from this graph? Yes you can.
    Can you find the force acting on the box from the acceleration. Again yes.
    Do you know of any other forces acting on the box? ie draw a FBD.
    Resolve your force(s) into x and y components and compute.
    remember -- > frictionless ramp.
  4. Oct 9, 2011 #3

    So I found that the acceleration is -2.5 m/s2. I then found that the theta (angle) is 14.47, which is, according to the site, true. Since the net force along the y component is 0 N, then according to Newton's law, N - mgsin@ = 0. (@ is theta). N is then 17.38 N.

    However, it is wrong according to the site. Anything wrong?

    Oh, and the mass is 7.1 not 7.6.
  5. Oct 10, 2011 #4


    User Avatar
    Gold Member

    Would not the force along the x-axis be mgsin@? And that is the force that slows the box down.
    If you drew the FBD, the normal force, N, would then be what.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook