Final answer:
The weight of the disk in a collision scenario is commonly assumed to be negligible when compared to the force of the collision. In collisions involving two objects, total momentum is conserved, assuming no external forces act on the system.
Step-by-step explanation:
The question assumes that the weight of the disk in the collision scenario is negligible compared to the force of the collision. This is typically an assumption made to simplify the calculations in physics problems, particularly in collisions where other forces, like the impact force, are significantly greater than the weight. Therefore, it's not necessary to consider the disk's weight when calculating the outcome of the collision.
In scenarios where two objects collide, such as two cars, the key principle is the conservation of momentum. Assuming no external forces like friction are acting on the system, the total momentum before the collision should be equal to the total momentum after the collision, regardless of the masses of the objects involved. This is because momentum is conserved in all elastic and inelastic collisions.