1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Solve for theta

  1. Mar 13, 2005 #1
    Here is the problem: The velocity of a 2.3 kg block sliding down a frictionless inclined plane is found to be 1.12 m/s. 1.20 sec. later it has a velocity of 5.08 m/s. What is the angle of the plane with respect to the horizontal?

    There is quite a bit of information here. I have gathered some of the vital details and will demonstrate what I have thus far, which may be correct or incorrect.

    This is a Newton's Second Law Problem (I believe).
    accel=v2-v1/t2-t1 = (5.08 - 1.12)/(1.2-0)= 3.3m/s^2
    So, at this point I have mass and acceleration to work with.
    I know that there are three forces acting on the block, so I have constructed a free body diagram.

    Also, solving for Fgrav would require w=m*g. w=(2.3)*(3.3) therefore w=22.545 [N].

    Most problems involving an inclined plane have theta given. However, I have not been able to find any problems similar to this one with theta unknown.

    Any help or website resources would be greatly appreciated.
  2. jcsd
  3. Mar 13, 2005 #2
    You have a right triangle. You can express two of the sides in terms of acceleration (m/s^2). Use a trig inverse property to solve for the angle. ([tex]arcsin(x)[/tex])
  4. Mar 13, 2005 #3
    [tex] F = mg sin \theta = m\frac{v_f - v_i}{t} [/tex]

    That's enough info! :P
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?