# Conservation of linear, angular momentum and energy in a collision

## Homework Statement

Mass 2 collides with mass 1 as shown in the image, mass 1 is attached to the stick and it is initially stationary. Consider that the stick is massless and can rotate around the point O. The entire system is on a frictionless table.
Which magnitudes are conserved in the system {m1,m2} before, during and after the collision?

Comments: no information is given (at this stage of the problem) about what kind of collision we are talking about.

## The Attempt at a Solution

Before the collision:

• External Forces sum up to zero-->Linear Momentum is conserved.
• For the same reason, angular momentum with respect to O is conserved.
• There are not any non conservative forces in the system-->Mechanical energy is conserved.
During the Collision:
• The bar exerts a force on the ball (Tension) --> linear momentum is not conserved.
• The tension is a central force --> Angular Momentum is conserved.
• The Tension is perpendicular to the movement of m2, so energy is conserved.
After the collision: I think it is exactly the same as during the collision, is this ok?

The next question is, in which direction does m2 move after the collision.

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