Which of the following quantities definitely changes when the reference frame changes in classical mechanics?

• A. The charge of an object
• B. The mass of an object
• C. The magnitude of the gravitational constant $G$
• D. The velocity of an object

Answer: (D)

Verified step by step guidance

1. Understand that in classical mechanics, certain physical quantities are invariant, meaning they do not change when you switch from one reference frame to another. Examples include intrinsic properties like charge, mass, and fundamental constants such as the gravitational constant \(G\).
2. Recall that the charge of an object is a fundamental property related to the number of protons and electrons it contains, and it remains the same regardless of the observer's frame of reference.
3. Recognize that the mass of an object, especially in classical mechanics (non-relativistic), is also invariant and does not depend on the observer's frame.
4. Note that the gravitational constant \(G\) is a universal constant and does not change with the choice of reference frame.
5. Identify that velocity, defined as the rate of change of position with respect to time, depends on the observer's frame of reference. Different observers moving relative to each other will measure different velocities for the same object.