AP Physics C: Mechanics / Unit 2: Force and Translational Dynamics
2.5 Newton's Second Law
Notes
$$\vec F_{net}=m\vec a$$
- Add all forces (with signs) to find the net force.
Practice
A 4 kg box has a 20 N net force. Its acceleration:
$\displaystyle \frac{20}{4}$.
30 N right and 10 N left on a 5 kg cart. Acceleration:
Net 20 N.
An elevator accelerates upward. The normal force on you is:
Net force must point up.
$F(t)=6t$ N acts on a 2 kg mass starting from rest. Its speed at $t=2$ s:
$a=3t$, so $\displaystyle v=\int_0^2 3t\,dt=6$.
Ready for more? Take the Unit 2 test.