Forces and Free-Body Diagrams - AP Physics 1

Tension equal to weight. Tension balances weight when elevator moves at constant velocity.

Electrostatic force. Coulomb force between charges; can be attractive or repulsive.

$f_k = 15 \text{ N}$. Using $f_k = \mu_k N = 0.3 \times 50 = 15 \text{ N}$.

$F_{\text{net}} = mg , \sin \theta - f$. Gravity component minus friction determines net acceleration down plane.

Friction doubles. Friction is directly proportional to normal force.

Gravitational force increases. Force is proportional to both masses in gravitational equation.

Directly proportional. From Newton's second law: $a = \frac{F}{m}$.

$f_s , \leq , \text{μ}_s N$. Static friction can vary up to maximum value $\text{μ}_s N$.

$N = 98 \text{ N}$. Normal force equals weight on horizontal surface: $N = mg$.

$F = -kx$. Hooke's law; negative sign indicates force opposes displacement.

Directly proportional. From Newton's second law: $a = \frac{F}{m}$.

$T = 49 \text{ N}$. At rest, tension equals weight: $T = mg = 5 \times 9.8 = 49 \text{ N}$.

$F_c = \frac{mv^2}{r}$. Force needed to maintain circular motion at constant speed.

Gravitational force. Earth's gravity provides centripetal force for orbital motion.

$f_k = 15 \text{ N}$. Using $f_k = \text{μ}_k N = 0.3 \times 50 = 15 \text{ N}$.

Normal force. Normal force provides upward support equal to object's weight.

$F_{\text{net}} = mg , \sin \theta - f$. Gravity component minus friction determines net acceleration down plane.

$N = mg , \cos \theta$. Normal force is weight component perpendicular to inclined plane.

Component of gravitational force parallel to the plane. Component $mg \sin \theta$ acts parallel to inclined surface.

Friction doubles. Friction is directly proportional to normal force.

Net force is 2 N in the direction of the larger force. Subtract opposing forces: $5 \text{ N} - 3 \text{ N} = 2 \text{ N}$.

For every action, there is an equal and opposite reaction. Forces always occur in equal and opposite pairs between objects.

$\text{N m}^2 \text{kg}^{-2}$. Units derived from $F = G \frac{m_1 m_2}{r^2}$ dimensional analysis.

$F = ma$. Force equals mass times acceleration; fundamental dynamics equation.

25 N in the direction of both forces. Add forces in same direction: $10 \text{ N} + 15 \text{ N} = 25 \text{ N}$.

Gravitational force. Gravity acts between all masses without physical contact.

Normal force. Normal force acts perpendicular to contact surfaces, preventing penetration.

Frictional force. Kinetic and static friction resist sliding between contact surfaces.

Frictional force. Friction always opposes relative motion between surfaces in contact.