How can I solve for the velocities of two balls after an off-center collision?

In summary: For the conservation of momentum, you use the initial momentum in the x and y directions and the magnitude of the velocities.
  • #1
TraceBusta
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A ball moving at 11 m/s makes an off-center elastic collision with another ball of equal mass that is initially at rest. The incoming ball is deflected at an angle of 30° from its original direction of motion. Find the velocity of each ball after the collision.

Ball moving initally at 11 m/s
(a) magnitude m/s (moving ball)?
(b) direction ° (from the original direction of motion)?

Ball initally at rest
(c) magnitude m/s?
(d) direction ° (from the original direction of motion)?

How do I start this problem? Someone in my recitation had a problem similar to this and used three equations with three unknowns. I think it was conservation of KE, conservation of momentum, and something else but i don't remember.

My book briefly talks about this, but there are no sample problems to work with.
Thanks
 
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  • #2
You have three equations: One conservation of energy and two for conservation of momentum (1 for the x direction and 1 for the y direction). Use the components of the velocity in the x and y directions for the conservation of momentum in the x and y direction, respectively. For the conservation of energy you just use the magnitude of the velocities.
 
  • #3
I'm having trouble setting up these equations. For conservation of energy, I have the initial KE, but final KE I don't know what the final kinetic energies of each ball is. I think the incoming ball is (1/2)m(11 m/s)^2*sin (30) but the final kinetic energy of the ball initially at rest I don't know what that is.
For the conservation of momentum, the initial momentum's are easy to calculate, but the final momentums are what I don't know (in both the x and y components) I have a feeling these type of questions will be on the exam coming up on Thurs. so I want to be able to understand how to do them.
Thanks
 

1. What is an off center collision?

An off center collision is a type of collision that occurs when two objects collide at a point other than their center of mass. This can result in rotational motion and can significantly affect the outcome of the collision.

2. How does an off center collision differ from a head-on collision?

In a head-on collision, the two objects collide at their center of mass, resulting in linear motion. In an off center collision, the objects collide at a point other than their center of mass, causing rotational motion.

3. What factors can influence the outcome of an off center collision?

The outcome of an off center collision can be influenced by various factors such as the size and shape of the objects, their velocities, and the angle at which they collide. The distribution of mass within the objects can also play a role.

4. Can an off center collision result in a perfectly elastic collision?

No, an off center collision cannot result in a perfectly elastic collision. This is because some of the kinetic energy will be converted into rotational energy due to the objects colliding at a point other than their center of mass.

5. How is the momentum conserved in an off center collision?

The total momentum of the system will still be conserved in an off center collision. However, the individual momenta of the objects may change as a result of their rotational motion. The sum of their linear and angular momenta will remain constant.

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