In our studies related to collisions, we have seen that during a collision of two bodies, the external forces, if any, are negligible compared to the internal ones, so the system can always be considered mechanically isolated. Let’s look at the figure above, where we have an oblique collision. In it we notice that after colliding, the masses take different directions from the initial direction.
In this situation, in which the collision is oblique , the velocities must be decomposed in only two directions. Then it suffices to apply, for each of the directions, the principle of conservation of momentum. As an example, consider two balls of the same mass m 1 and m 2 and speeds v 1 and v 2 , respectively, which collide. In the figure above we have the representation of the balls before and after the collision.
Decomposing the velocities of the two masses in the horizontal and vertical direction, for each of the directions, the conservation of momentum, we have:
– horizontal direction:
– vertical direction:
For the solution to be possible with these two equations, we must have at most two unknowns.