NEWTON'S FIRST LAW
- Every body continues in its state of rest, or of uniform motion in
a straight line, unless it is compelled to change that state by forces
impressed upon it.
NEWTON'S THIRD LAW
- Whenever one body exerts a force on another, the second always exerts
on the first a force which is equal in absolute magnitude, opposite in
direction, and has the same line of action.
- Note: Action-reaction forces act on different bodies
NEWTON'S SECOND LAW: Fnet
- If there is an unbalanced force on an object, we find that the
VELOCITY of the object changes. There is an acceleration.
- We find that Fnet , the unbalanced force, is proportional
to the acceleration, a
- The proportionality factor is the mass, m.
- Fnet = ma
- Here Fnet is the vector sum of all forces acting
on the object.
- The units are [lbs] = [slugs][f/s2] or [newtons] = [kg][m/s2]
MASS AND WEIGHT
- The weight of an object is the force of attraction between the
earth and the object
- Weight is proportional to the acceleration of gravity
- W = mg
- Since the acceleration of gravity may be different for different planets,
weight may be different for different locations. However, for a given object
the rest mass is constant.