Fg
weight or force of gravity (N)
g
gravitational field strength (N/kg or m/s²)
r (forces)
distance between the centers of two masses (m)
r (orbits)
distance from the center of the planet to the orbiting object (m)
G
Gravitation constant (Nᐧm²/kg²)
θ (motion)
angular position (rad)
Δθ
angular distance (rad)
ω
angular velocity: rate of change of angular position (rad/s)
α
angular acceleration: rate of change of angular velocity (rad/s²)
∆x or s
arc length or circular distance (m)
vT
tangential velocity (m/s)
aT
tangential acceleration: changes the speed; points tangentially forward/backward (m/s²)
ac
centripetal acceleration: changes the direction; points towards the center (m/s²)
τ
torque (Nᐧm)
θ (torque)
angle between moment arm and force (°)
Rotational equilibrium
Net torque = 0; angular acceleration = 0
Translational equilibrium
Net force = 0; acceleration = 0
18 Static equilibrium
Net torque and net force = 0; no acceleration
I (rotation)
moment of inertia: resistance to CHANGE in angular motion (kgᐧm²)
r (rotation)
distance from pivot point to force or object (m)
L
angular momentum (kgᐧm²/s)
ΔL (effect)
angular impulse: change in angular momentum (kgᐧm²/s)
Jrot (cause)
angular impulse: an external torque applied for a time interval (Nmᐧs)
Krot
rotational kinetic energy (J)
The moment of inertia of an object about an axis
I=mr²
Relating rotational and linear variables:
(1) ∆x=∆θr (2) v=ωr (3) a=αr