Question

an experiment is conducted to determine how the arm length of a pendulum affects its period. the experimental design calls for varying the length of the arm and the mass of the bob. which is true about this experiment, based on good experimental design? only the mass should be changed. the arm length should remain the same. the force applied to the mass should be varied for each trial. only the arm length should be changed. the mass should remain the same. the material the arm is made of should be varied for each trial.

Explanation:

In a good - experimental design, when studying the effect of one variable (here, arm length of a pendulum on its period), other variables should be controlled. Since the goal is to determine how arm length affects the period, the mass of the bob should be kept constant as it is not the variable of interest in this relationship. Changing multiple variables simultaneously makes it difficult to determine which variable is causing the observed changes in the period.

Answer:

Only the arm length should be changed. The mass should remain the same.