18. describe the relationship between kinetic energy and mass, and give an example of
how changing an object's mass changes its kinetic energy.

Kinetic energy is directly proportional to mass

Explanation:

Kinetic energy is directly proportional to the mass of an object and also directly proportional to the square of the velocity of that object:

Notice that if we keep velocity constant and only increase the mass of a object, the kinetic energy of that object would increase, as we've already emphasized the direct relationship between the kinetic energy term and the mass term.

Let's take a simple example: assume that object 1 and object 2 are both moving at the same velocity but object 1 has a much lower mass than object 2. According to the equation, object 1 has lower kinetic energy. This object can then transform all of its kinetic energy into some other form, say, heat the ground. The heat transferred will be significantly lower than by the object 2 moving at the same velocity but having a much greater mass.