In this section, we collect together all the important formulas from the preceding sections, and summarize the equations that we use to analyze motion of a rigid body.
We consider motion of a rigid body that has mass density ρ during some time interval t0 < t < t1 , and define the following quantities:
6.6.1 Forces, torques, impulse, work, power

- The total force acting on the body

- The total linear impulse exerted by forces during the time interval

- The total moment (including torques) acting on the body

- The tot al angular impulse exerted on the body during the time interval

- The rate of work done by forces and torques acting on the body

- The total work done by forces and torques on the body during the time interval

6.6.2 Inertial properties
- The total mass is

- The position of the center of mass is

- The mass moment of inertia about the center of mass

where d = r − rG
For a 2D body with mass per unit area µ we use

- The total mass is

- The position of the center of mass is

- The mass moment of inertia about the center of mass is

where d = r − rG
6.6.3 Describing motion
- The rotation tensor (matrix) maps the vector connecting two points in a solid before it moves to its position after motion rB − rA = R(pB − pA)

- The spin tensor is related to R by


- Rotation through an angle θ about an axis parallel to a unit vector n = nx i +ny j + nzk is
- The angular velocity vector ω = ω x i +ωy j+ ω zk is related to W by
- The angular acceleration vector is α = dω/dt
- The velocities of two points A and B in a rotating rigid body are related by v B −v A = ω ×(rB − rA )
- The accelerations of A and B are related by aB − aA = α ×(rB−rA) + ω×(vB − vA) = α ×(rB−rA) + ω× ω×(rB−rA)]
6.6.4 Momentum and Energy
- The total linear momentum is p = MvG
- The angular momentum (about the origin) is h =rG × MvG+ IG ω
- The total kinetic energy is T= 1/2 MvG ·vG +1/2 ω·IGω
For 2D planar problems, we know ω = ωzk . In this case, we can use
- The total linear momentum is p = MvG
- The total angular momentum (about the origin) is h =rG × MvG+IGzzω z k
- The total kinetic energy is

6.6.5 Conservation laws
- Linear momentum


- Angular momentum

- Work-Power - Kinetic Energy relation

- Energy equation for a conservative system d/dt (T+V) =0 T0+ V0= T1+V1