Final answer:
In the provided physics experiment, notable variables include the length of the string, mass of the tennis balls, and air resistance, and the kinematic equations involve acceleration, displacement, time, and velocity.
Step-by-step explanation:
The variables in an investigation involving throwing two tennis balls tied together with a string include potentially multiple factors. However, based upon the information provided within the context of the experiment, the notable variables are likely to be the length of the string, the mass of the tennis balls, and the air resistance. These factors would likely have an impact on the observed ballistic trajectory of the tennis balls when they are thrown.
In an experiment where one marks the center of the string with bright ink or a brightly colored sticker, the variables under consideration do not change; instead, the marking serves to make the center of mass visible, thereby aiding in observational analysis.
When considering kinematic equations, the four variables of importance are acceleration, displacement, time, and velocity. These variables play essential roles in determining the motion of objects under the forces imparted upon them.