Final answer:
The best dependent variable for a simple pendulum experiment is the period, which depends on string length and gravity but not mass or swing amplitude.
Step-by-step explanation:
In conducting an experiment with a simple pendulum, the dependent variable should ideally be something that you expect to change as a result of manipulations of other variables. The period of a pendulum is dependent on factors such as the length of the string and the acceleration due to gravity, and it is independent of the mass of the pendulum bob and the amplitude of the swing, especially if the swing angle is less than about 15°. Hence, the period would be the best choice for the dependent variable in a pendulum experiment because it is what you would typically measure and observe how it changes with different lengths of the string or different values of gravitational acceleration.
The period of a pendulum is particularly interesting because it provides a direct way to measure the acceleration due to gravity if the length of the pendulum is known. This simplicity makes period a variable of interest in many physics experiments, demonstrating the pendulum's utility in scientific studies.