Question

7. which of the following statements are true?
a. kinetic energy must be a positive quantity
b. kinetic energy may be either a positive or negative quantity
c. potential energy must be a positive quantity
d. potential energy may be either a positive or negative quantity
e. the potential energy of a system must be equal to its kinetic energy

Answer 1

Since Kinetic energy depends upon mass, which is a positive quantity, and square of velocity, which is again a positive quantity. So Kinetic energy can never be negative.

Potential Energy depends upon reference. If the body is above the reference, potential energy will be positive and vice versa. So it can either be positive or negative.

Again, Potential energy of a body need not be equal to it's Kinetic energy at all times, rather the Total Energy must be conserved.

Thus, only options (a) and (d) are correct.