Question

how does friction affect the energy of a moving object?
a. it reduces its kinetic energy
b. it increases its potential energy
c. it increases its mass

Explanation:

Friction acts opposite to the direction of motion of a moving object. Kinetic energy is the energy of motion ($KE=\frac{1}{2}mv^{2}$, where $m$ is mass and $v$ is velocity). When friction acts on a moving object, it does negative work on the object. According to the work - energy theorem ($W=\Delta KE$), negative work done on an object reduces its kinetic energy. Potential energy ($PE = mgh$, where $h$ is height) is related to the position of an object in a gravitational (or other potential) field. Friction does not affect the height (in a simple translational motion on a horizontal surface, for example) or the mass of an object. Mass is an intrinsic property of an object and is not changed by the force of friction.

Answer:

A. It reduces its kinetic energy