AP Physics C: Mechanics Flashcards: Torque
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.
What does it mean for the torque vector to be 'normal' to the plane defined by vectors $\vec{r}$ and $\vec{F}$?
It means the torque vector is perpendicular to the plane that contains both the position vector and the force vector.
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What does it mean for the torque vector to be 'normal' to the plane defined by vectors $\vec{r}$ and $\vec{F}$?
It means the torque vector is perpendicular to the plane that contains both the position vector and the force vector.
In the torque equation $\vec{\tau}=\vec{r}\times\vec{F}$, what do $\vec{r}$ and $\vec{F}$ represent?
$\vec{r}$ is the position vector from the chosen pivot point to where the force is applied, and $\vec{F}$ is the force vector being exerted on the rigid system.
What is a cross product?
The cross product between two vectors, $\vec{A}$ and $\vec{B}$, results in a new vector quantity that is perpendicular to both original vectors.
What are the two primary tasks related to torques on a rigid system mentioned in the content?
The two primary tasks are to identify the torques exerted on a rigid system and to describe the torques exerted on that system.
What is the direction of the torque vector relative to the position and force vectors?
The direction of the torque vector is perpendicular to both the position vector ($\vec{r}$) and the force vector ($\vec{F}$), making it normal to the plane defined by those two vectors.
If a force is applied parallel to the position vector from the pivot point, what is the magnitude of the torque?
The magnitude of the torque is zero. This is because the angle θ between the vectors is 0, and the magnitude calculation $|\vec{\tau}|=rF\sin(0)$ results in 0.
How is the magnitude of a vector resulting from a cross product, such as torque, calculated?
The magnitude is calculated as $|\vec{A}\times\vec{B}|=AB\sin\theta$, where A and B are the magnitudes of the vectors and θ is the angle between them.
To maximize torque with a given force, at what angle should the force be applied relative to the position vector?
The force should be applied perpendicularly (θ = 90°) to the position vector, as this makes $\sin\theta=1$, maximizing the magnitude of the cross product.
How would you describe the torque exerted on a rigid system?
The torque is described by its vector nature, calculated as the cross product of the position vector and the applied force vector ($\vec{\tau}=\vec{r}\times\vec{F}$).
What is the formula for the torque exerted on a rigid system by a given force?
The torque exerted on a rigid system about a chosen pivot point by a given force is described by the cross product equation $\vec{\tau}=\vec{r}\times\vec{F}$.