Sir Isaac Newton

·     Discovered a link between the force on an object, it’s mass, and it’s acceleration

Force

·     Needed to change motion

·     Has the ability to change motion

·     A push or a pull or any action that has the ability to change motion

Units of force: pounds or Newtons

1 N = 0.228 lbs

1 lb = 4.48 N

FIRST LAW:

An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

·       Newton's first law of motion declares that a force is not needed to keep an object in motion.

Free-Body Diagram:

When forces are balanced we call this equilibrium.

Now consider a book sliding from left to right across a table top. The book is in motion and at the moment there is no one pushing it to the right. (Remember: a force is not needed to keep a moving object moving to the right.)

Unbalanced forces cause accelerations.
 

Difference between force and mass:

·     Force is a push or pulling action that can change motion

·     Mass is the amount of “stuff” or matter in an object and is a basic property of objects

·     Mass resists the action of forces by making objects harder to accelerate

Inertia

·     The property of an object to resist changing its state of motion

·     Is a property of mass

o The amount of inertia an object has depends on its mass

·     An object with a lot of inertia takes a lot of force to start or stop

o Big trucks have more inertia than small cars, so it is much harder to push a truck than a car.