In an elastic collision, the following is conserved:
- Momentum: The total momentum of the system before the collision is equal to the total momentum after the collision.
Inelastic collisions also conserve momentum, but kinetic energy is not conserved in inelastic collisions. However, in elastic collisions, both momentum and kinetic energy are conserved.
To address the other options:
- Time is not a conserved quantity in the context of collisions.
- Force is not a conserved quantity; it can change during interactions.
- Information is not typically referred to as conserved in physics in this context.
So the correct answer is Momentum.