The kinetic energy of an object is directly proportional to its velocity squared. This means that if the velocity of a moving car is halved, its kinetic energy would decrease significantly.

Explanation:
1. Kinetic Energy Formula: The formula for kinetic energy is KE = 1/2 * m * v^2, where KE is the kinetic energy, m is the mass of the object, and v is the velocity of the object.
2. Halving the Velocity: If the velocity of the car is halved, it means that the new velocity (v') is equal to half of the original velocity (v/2).
3. Calculation: Substituting the new velocity into the kinetic energy formula, we get KE' = 1/2 * m * (v/2)^2 = 1/2 * m * v^2/4 = KE/4.
4. Conclusion: We can see that the new kinetic energy (KE') is equal to one-fourth of the original kinetic energy (KE). Therefore, when the velocity of a moving car is halved, its kinetic energy becomes one-fourth of what it was originally.

Example:
Let's consider an example to illustrate this concept. Suppose a car has a mass of 1000 kg and is initially moving at a velocity of 20 m/s.
- The initial kinetic energy of the car can be calculated using the formula KE = 1/2 * m * v^2 = 1/2 * 1000 kg * (20 m/s)^2 = 200,000 J.
- If the velocity of the car is halved, the new velocity becomes 10 m/s.
- The new kinetic energy can be calculated using the formula KE' = 1/2 * m * (v/2)^2 = 1/2 * 1000 kg * (10 m/s)^2 = 50,000 J.
- Comparing the initial kinetic energy with the new kinetic energy, we can see that the new kinetic energy is one-fourth (1/4) of the original kinetic energy.

Therefore, the correct answer is option C - the kinetic energy would become one-fourth if the velocity of a moving car is halved.