Game Development Reference
InDepth Information
D'Alembert's principle also applies to rotations:
τ
=
τ
i
i
which include the torques generated from offcenter forces.
The separating velocity of two colliding objects
v
s
is related to their velocity im
mediately before the collision
v
c
by
v
s
=−
cv
c
where
c
is the coefficient of restitution.
D.6
O
THER
F
ORMULAE
Hook's law relates the force of a spring
f
to its length:
k

l
0
d
f
=−
d
−
where
d
is the vector from one end of the spring to another.
Simple fluid flow can be modeled with an aerodynamic tensor:
f
a
=
A
v
w
where
f
a
is the resulting force,
A
is the aerodynamic tensor, and
v
w
is the velocity of
the air.