What does the mechanical advantage of a first-class lever depend upon? Describe how it can be changed?

Hint:There are three classes of lever: first, second and third. These classes are based on the position of pivot in the pivot, effort and load system. If the fulcrum is closer to the load than to the input force then the mechanical advantage is greater than one.

Complete answer:
Let's first understand the three classes of lever:

First class lever: In the first-class lever, the fulcrum is placed closer to the effort, then more effort is needed to move the load to a greater distance. Examples of first-class levers are: teeter-totter, a car jack, and a crowbar.

Second-class lever: In the second-class levers, the load is located between the effort and the fulcrum. When the load is closer to the fulcrum as compared to the effort, then effort required will be lesser to move the load. If the load is closer to the effort than the fulcrum, then the effort required more be more to move the load.

Third-class levers: In the third-class levers, the input force is placed between the output force and the fulcrum. Examples: Baseball bat. The handle of the baseball bat is the fulcrum, the input force is supplied near the middle, and the other end of the bat that pushes the ball with the output forces.

Mechanical advantage of first-class levers depends on the position of the load, fulcrum and the effort.The maximum mechanical advantage is when the fulcrum is closer to the load than to the input force.

In order to change the mechanical advantage of the first-class lever, we can opt the following:
-Move the fulcrum closer to the load, this will increase the mechanical advantage.
-Move the effort farther away from the fulcrum, this will increase the mechanical advantage.
This may require a longer lever.

Note: The mechanical advantage is equal to one when the fulcrum is exactly in the middle of the load and the input force. When the fulcrum is closer to the input force, the mechanical advantage has the least value.