Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[EX Q]: Question: Intensity is defined to be the power per unit area carried by a what? Answer: wave
[EX A]: Intensity is defined to be the power per unit area carried by a wave. Power is the rate at which energy is transferred by the wave. In equation form, intensity I is.

[EX Q]: Question: Individuals with sickle cell anemia have crescent-shaped what? Answer: red blood cells
[EX A]: Figure 39.21 Individuals with sickle cell anemia have crescent-shaped red blood cells. (credit: modification of work by Ed Uthman; scale-bar data from Matt Russell).

[EX Q]: Question: If a machine only changes the direction of a force without changing the ratio of the output/input forces, then what is its associated mechanical advantage? Answer: 1
[EX A]:
For machines that change only the direction of the force, such as the rope systems on flagpoles, the output force is the same as the input force. Therefore, the mechanical advantage is equal to 1.