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View Full Version : Motion of an equalateral triangle, differenciating


printz0r
Oct 24, 2009, 05:01 PM
I am doing a advanced physics problem where I have an equilateral triangle with all of its corners connected to a wheel. The triangle is sitting up right on 2 wheels. It has sides of .2m The wheel to the right is being lifted at a constant rate of .3 m/s. Which causes the wheel on the left to move in the x direction only. The question asks to solve for the angular velocity of the triangle.

The book starts the problem saying that x^2 +y^2 = b^2. They differentiate which leads to x(dx/dt) + y(dy/dt) = 0. How does that differential work, + how do you solve the rest of the problem?

Unknown008
Oct 24, 2009, 11:40 PM
I don't quite understand what is happening, but I know how they got that differential equation.

x^2 + y^2 = b^2

Differentiate with respect to t:

2x \frac{dx}{dt} + 2y \frac{dy}{dt} = 0

I guess b is a constant here.

Factorise 2:

2(x \frac{dx}{dt} + y \frac{dy}{dt}) = 0

That means;

(x \frac{dx}{dt} + y \frac{dy}{dt}) = \frac02

x \frac{dx}{dt} + y \frac{dy}{dt} = 0

Could you try posting a picture?