AP Physics C: Mechanics Flashcards: Rotational Equilibrium and Newton's First Law in Rotational Form
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.
Under what specific condition will a system's angular velocity remain constant?
A system's angular velocity will remain constant only if the net torque exerted on the system is zero.
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Under what specific condition will a system's angular velocity remain constant?
A system's angular velocity will remain constant only if the net torque exerted on the system is zero.
What does the term 'net torque' refer to?
Net torque is the vector sum of all individual torques exerted on a system.
What is rotational equilibrium?
Rotational equilibrium is a state in which the net torque exerted on a system is zero.
What is the mathematical equation that defines rotational equilibrium?
The equation for rotational equilibrium is $\sum\vec{\tau}_{i}=0$, which signifies that the vector sum of all torques on the system is zero.
What is the rotational analog of Newton's first law?
The rotational analog of Newton's first law states that a system will maintain a constant angular velocity only if the net torque exerted on it is zero.
How are rotational equilibrium and constant angular velocity related?
A system is in rotational equilibrium (zero net torque) if and only if its angular velocity is constant.
If a spinning bicycle wheel is in rotational equilibrium, what must be true about its angular velocity?
If the wheel is in rotational equilibrium, the net torque is zero, therefore its angular velocity must be constant.
What does a net torque of zero imply about a system's rotational state of motion?
A net torque of zero implies the system's rotational state of motion is not changing, meaning its angular velocity is constant.
A door is being pushed with equal force on the handle and pulled with equal force on the other side of the handle, causing it to remain stationary. Is the door in rotational equilibrium?
Yes, because its angular velocity is constant (at zero), the net torque on the door must be zero, placing it in rotational equilibrium.
A planet orbits the sun at a constant angular velocity. Assuming no other forces, what can you conclude about the net torque on the planet?
Since the planet's angular velocity is constant, according to the rotational form of Newton's first law, the net torque exerted on it must be zero.