AP Physics C: Mechanics Flashcards: Rotational Inertia
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
How is rotational inertia for a solid with a continuous mass distribution calculated?
For a solid considered as a collection of differential masses (dm), its rotational inertia is calculated using the integral equation I = ∫r²dm.
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How is rotational inertia for a solid with a continuous mass distribution calculated?
For a solid considered as a collection of differential masses (dm), its rotational inertia is calculated using the integral equation I = ∫r²dm.
How does rotational inertia change when the axis of rotation does not pass through the system's center of mass?
When a rigid system rotates about an axis not passing through its center of mass, the rotational inertia is greater than its inertia about a parallel axis through the center of mass.
In the equation I = ∫r²dm, what does the variable 'r' represent?
The variable 'r' represents the perpendicular distance of each differential mass element (dm) from the given axis of rotation.
According to the parallel axis theorem, what axis of rotation results in the minimum rotational inertia for a rigid system?
The rotational inertia of a rigid system is at its minimum value when the axis of rotation passes through the system's center of mass.
Identify the meaning of each variable in the parallel axis theorem: I' = I_cm + Md².
I' is the inertia about the new axis, I_cm is the inertia about the center of mass, M is the total mass, and d is the perpendicular distance between the two parallel axes.
What is the physical interpretation of the term Md² in the parallel axis theorem?
The term Md² represents the rotational inertia of a point mass M located at a distance d from the axis of rotation, accounting for the additional inertia from rotating about that displaced axis.
What is rotational inertia?
Rotational inertia describes the resistance of a rigid system to a change in its rotational motion relative to a given axis of rotation.
A rigid body has rotational inertia I_cm about its center of mass. What is its rotational inertia I' about a parallel axis located a distance 'd' away?
The new rotational inertia is given by the parallel axis theorem: I' = I_cm + Md², where M is the total mass of the body.
What is the Parallel Axis Theorem?
The parallel axis theorem is a formula used to find the rotational inertia of a rigid system about any axis that is parallel to an axis passing through its center of mass.
State the equation for the Parallel Axis Theorem.
The equation is I' = I_cm + Md², where I_cm is the inertia about the center of mass, M is the total mass, and d is the distance between the parallel axes.