An elastic collision conserves

Options

A. kinetic energy but not momentum
B. momentum but not kinetic energy
C. neither momentum nor kinetic energy
D. both kinetic energy and momentum

Answer

To solve the question "An elastic collision conserves:", we need to analyze the properties of elastic collisions in physics.

### Step-by-Step Solution:

1. **Definition of Elastic Collision**: An elastic collision is defined as a collision in which both kinetic energy and momentum are conserved. This means that the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision, and the same applies to momentum.

2. **Conservation of Kinetic Energy**: In an elastic collision, the kinetic energy before the collision is equal to the kinetic energy after the collision. Mathematically, if two objects collide elastically, the equation can be expressed as:
\[ KE_{initial} = KE_{final} \]
where \( KE = \frac{1}{2}mv^2 \).

3. **Conservation of Momentum**: Similarly, momentum is also conserved in elastic collisions. The total momentum before the collision is equal to the total momentum after the collision. This can be expressed as:
\[ p_{initial} = p_{final} \]
where momentum \( p = mv \).

4. **Conclusion**: Since both kinetic energy and momentum are conserved in elastic collisions, the correct answer to the question is:
- **D) both kinetic energy and momentum**.

### Final Answer:
**D) both kinetic energy and momentum**