AP Physics C: Mechanics / Unit 2: Force and Translational Dynamics
2.10 Circular Motion
Notes
Moving in a circle at constant speed still means acceleration toward the center:
$$a_c=\frac{v^2}{r},\qquad F_{net}=\frac{mv^2}{r}$$
- The centripetal force is provided by a real force (tension, friction, gravity, normal).
Practice
A car turns on a flat road. The centripetal force comes from:
Tires grip the road.
Doubling speed in the same circle makes $a_c$:
$v^2$.
$v=10$ m/s, $r=5$ m. $a_c=$
$\displaystyle \frac{100}{5}$.
A mass on a string swings in a vertical circle. At the bottom, tension is:
Net force points up toward the center.
Ready for more? Take the Unit 2 test.