AP Physics 1 / Unit 5: Torque and Rotational Dynamics
5.5 Rotational Equilibrium and Newton's First Law in Rotational Form
Notes
An object is in rotational equilibrium when the net torque is zero: $\displaystyle \sum\tau=0$. It then rotates at constant $\omega$ (or stays at rest).
- Full equilibrium: $\displaystyle \sum F=0$ and $\displaystyle \sum\tau=0$.
Practice
A seesaw balances with 300 N at 2 m on one side. On the other side, 400 N must sit at:
$300(2)=400d$.
A wheel spinning at constant $\omega$ has net torque:
No angular acceleration.
For a beam in static equilibrium:
No acceleration of either kind.
Ready for more? Take the Unit 5 test.