If several forces act on an object, then we can add all of them to
obtain the net force. The net force, net,
which may be the sum of many forces (each of which is labeled by i as
i = 1, 2, ... , n) acts as one single force
The individual forces can be:
- Contact forces
- Examples are: pushing, kicking, lifting, pulling, ...
- Objects need to be in direct physical contact with each
other to exert these kinds of forces on each other.
- Examples are: gravity, magnetism, electrostatic attraction,
... The only one of these that interests us for now is gravity,
the other action-at-a-distance forces will only appear in the
second semester of this course.
- These action-at-a distance forces occur when the objects
exerting these forces on each other are not in direct contact
with each other. Instead these forces are transmitted by
exchanging particles. (How this exactly works is not really
relevant here and will be discussed in the second semester of