A particle moves in a circle with a constant speed $v$. Which of the following quantities remains constant?

Solution

1. Kinetic energy is defined as $K=\frac{1}{2}m{v}^2$.
2. Since the speed $v$ is constant and mass $m$ is constant, $K$ remains constant.
3. Velocity, acceleration, and momentum are vectors that change direction during circular motion.
4. Hence the answer is (C).