Question

which one of the following statements concerning kinetic energy is true? a. kinetic energy is always positive. b. kinetic energy is always equal to the potential energy. c. kinetic energy is directly proportional to velocity. d. kinetic energy is a quantitative measure of inertia. e. kinetic energy can be measured in watts.

Explanation:

• Kinetic energy is given by $K = \frac{1}{2}mv^{2}$, where $m>0$ (mass is non - negative) and $v^{2}\geq0$. Since mass is a non - negative quantity and the square of velocity is non - negative, kinetic energy is always non - negative. In non - zero motion cases, it is positive.
• There is no general rule that kinetic energy equals potential energy.
• Kinetic energy $K=\frac{1}{2}mv^{2}$ is proportional to the square of velocity, not velocity directly.
• Inertia is measured by mass, not kinetic energy.
• The unit of kinetic energy is joules, not watts (watts is the unit of power).

Answer:

A. Kinetic energy is always positive.