Game Development Reference
In-Depth Information
Figure 5-7.
Newton's second law scalar equations
Newton's third law:
External forces on objects occur in pairs. That is, if body 1
collides with body 2, it exerts a force on body 2. Body 2 also exerts an equal but
opposite force on body 1. (See Figure
5-8
.)
Body 1
-F
F
Body 2
Figure 5-8.
Newton's third law demonstrated by colliding spheres
Gravity
The earth's gravity is also a force that can act on objects. For example, Newton's second law can be
altered to refer to the earth's gravity. The weight of an object on the earth is actually a force that is
equal to the mass of the object, multiplied by the gravitational acceleration or free fall acceleration at
the location of the object. (See Figure
5-9
.)
Weight = Mass
*
Free Fall Acceleration
W = mg
Figure 5-9.
Force of gravity
