AP Physics 1 / Unit 2: Force and Translational Dynamics
2.1 Systems and Center of Mass
Notes
A system is the object(s) you choose to analyze. Its center of mass moves as if all external forces act there.
$$x_{cm}=\frac{\sum m_ix_i}{\sum m_i}$$
Practice
2 kg at $x=0$ and 6 kg at $x=4$ m. $x_{cm}=$
$\displaystyle \frac{0+24}{8}$.
Internal forces in a system:
Only external forces matter.
The center of mass is always closer to:
Weighted average.
Ready for more? Take the Unit 2 test.