AP Physics Unit 12 Variables

Unit 12 Variables

Weight or force of gravity (N)

Fg

Gravitational field strength (N/kg or m/s^2)

g

Distance between the centers of two masses (m)

r (forces)

Distance from the center of the planet to the orbiting object (m)

r (orbits)

Gravitation constant (EC: 6.67x10^-11 N*m^2/kg^2)

G

Angular position (rad)

θ (motion)

Angular distance (rad)

Δθ

Angular velocity: rate of change of angular position (rad/s)

ω

Angular acceleration: rate of change of angular velocity (rad/s^2)

α

Arc length or circular distance (m)

Δx or s

Tangential velocity (m/s)

V(t)

Tangential acceleration; changes the speed; points tangentially forward/backward (m/s^2)

a(t)

Centripetal acceleration: changes the direction; points towards the center (m/s^2)

a(c)

Torque (N*m)

τ

Angle between moment arm and force (°)

θ (torque)

Net torque=0 => angular acceleration=0 (Ignore)

Rotational Equilibrium

Net force= 0 => acceleration = 0 (Ignore)

Translational Equilibrium

Net torque and net force= 0 => no acceleration (Ignore)

static equilibrium

moment of Inertia: resistance to CHANGE in angular motion (kg*m^2)

I (rotation)

Distance from pivot point to force or object (m)

r (rotation)

Angular momentum (kg*m^2/s)

L

Angular impulse: change in angular momentum (kg*m^2/s)

ΔL (effect)

Angular impulse: an external torque applied for a time interval (N*m/s)

J(rot) (cause)

Rotational kinetic energy (J)

K(rot)

I=mr^2

The moment of inertia of an object about an axis:

Δx= Δθr ; v=ωr ; a=αr

Relating rotational and linear variables: