Question

Identify the conditions for an elastic collision in a closed system. Check all that apply.

Energy is conserved.
Velocities may change.
Momentum is conserved.
Kinetic energy is conserved.
Objects stick together after the elastic collision.
One object may be stationary before the elastic collision.

Answer 1

Correct answers: Energy is conserved (with clarification), Velocities may change, Momentum is conserved, Kinetic energy is conserved, One object may be stationary before the elastic collision.

Brief justification:
- Energy is conserved — True: in any closed system total energy is conserved. For an elastic collision this specifically means mechanical (kinetic) energy is conserved (no conversion to heat or deformation energy).
- Velocities may change — True: individual object velocities generally change in a collision even though total momentum and kinetic energy are conserved.
- Momentum is conserved — True: in a closed system with no external forces, linear momentum is conserved.
- Kinetic energy is conserved — True: that is the defining property of an elastic collision (kinetic energy before = kinetic energy after).
- Objects stick together after the elastic collision — False: sticking is the defining feature of a perfectly inelastic collision, not an elastic one.
- One object may be stationary before the elastic collision — True: it is allowed (e.g., a moving particle colliding with a stationary one).