An elastic collision in two dimensions

Thread starter Woopy
Start date Dec 6, 2008
Tags

Collision Dimensions Elastic Elastic collision Two dimensions

Click For Summary

The discussion revolves around solving an elastic collision problem in two dimensions, focusing on the conservation of momentum in both x and y directions. Participants emphasize the need to calculate momentum components rather than just magnitudes, which leads to confusion about signs and directions. The conversation includes calculations for initial and final momentum for two objects, with specific attention to the angles and velocities involved. Participants also discuss how to derive kinetic energy from the velocities, noting that the final speed of one object remains an unknown that can be solved through momentum equations. The thread highlights the complexity of the problem and the necessity for careful component analysis in two-dimensional collisions.

Dec 7, 2008

Doc Al

Mentor

Note that when you calculate the KE, you are already given the speeds for the particles before the collision and the speed of the green particle after the collision. So for them there is no need to use components, just use KE = 1/2mV^2, where V is the given speed of the particle.

For the speed of the red particle after the collision, you'll have to figure that out. Using momentum equations, you can solve for Vx & Vy for that particle. Then you can calculate its KE either by first finding the total speed (V^2 = Vx^2 + Vy^2) or just by using the components of its velocity:
KE = 1/2mV^2 = 1/2mVx^2 + 1/2mVy^2.