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: Finding velocity of an object moving down a incline with a non constant acceleration

  1. Sep 29, 2010 #1
    1. The problem statement, all variables and given/known data
    An object rests at the top of a frictionless incline with length L and angle θo. At the moment the object is released the angle begins to decrease at a constant rate w. Thus the angle as a function of time is θ(t)= θo-wt. Value of w is defined to be the rate such that at the instant the object reaches the bottom of the incline, θ(t)=0. Find the objects velocity when it reachs the bottom of the incline in terms of L, θo, and the gravitational constant.

    2. Relevant equations


    3. The attempt at a solution
    I tried solving this by using the equation 〖Vf〗^2=[Vo]^2+2a∆x, with Vo=0 and ∆x=L.
    I solved for a by adding up the forces moving in the x direction giving me: a= gsinθ. I plugged this in and got the answer Vf=(2(gsin(θ))(L))^(1/2) but I was wrong. The answer is (√Lg(1-cos(θ)))/(√(sin⁡〖θ_o-θ_o cos⁡〖θ_0 〗 〗 )
    I don't understand where to even begin with this problem, please help me!
  2. jcsd
  3. Oct 1, 2010 #2
    Re: Finding velocity of an object moving down a incline with a non constant accelerat

    You have to set up and integrate the equations of motion. The equation you are using only applies to constant acceleration.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook