NEWTON’S THREE LAWS Newton's 1 st Law: the Law of Inertia: An object at rest tends to stay at rest, and an object in motion tends to stay in motion. or, An object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an unbalanced force.

NEWTON’S THREE LAWS KEY POINTS: 1. Objects resist changes in their state of motion; they are said to have inertia. 2. Establishes the concept of an inertial reference frame.

NEWTON’S THREE LAWS DEFINITIONS: Inertia: a measure of an object's resistance to changes in its motion. Mass (not weight): a measure of the amount of material in an object; a quantitative measure of inertia

NEWTON’S THREE LAWS Inertial reference frame: A region where Newton’s 1 st Law holds true. For example, if your car is moving straight at a steady 30 mph, that would be an inertial reference frame. Once you apply brakes, it is no longer an inertial reference frame until you either stop or continue at a different steady speed.

NEWTON’S THREE LAWS USS Nimitz: Length: 332m (1092 feet) Beam (width): 40.8m (134 feet) Mass: 86,183,000 kg (190 million lbs) Speed: 15 meters/second (34 mph) We suspect this object, having a large mass, would strongly resist a change in its motion. So if the carrier is moving at 34 mph and shuts its engines down, how far will it drift? A thousand feet? A mile?

NEWTON’S THREE LAWS In turns out that the stopping distance (in a smooth sea) would be about 32 km (20 miles) if no active measures are taken to stop the forward motion of the carrier (such as reversing the engines).

NEWTON’S THREE LAWS Newton's 2 nd Law: the Law of Proportionality: The acceleration of an object is directly proportional to the net force and inversely proportional to its mass.

NEWTON’S THREE LAWS Expressed formally: Where F i = one of many forces on the object, m = the object's mass, and a = the resulting acceleration.

NEWTON’S THREE LAWS KEY POINTS: 1.An object will accelerate if there is an unbalanced (or net) force 2.The acceleration is always in the direction of the net force.

NEWTON’S THREE LAWS DEFINITIONS: Force: a push or a pull on an object; an influence on an object that can change the object’s motion if the object is free to move, or change the object’s configuration if the object can’t move. Mass: a measure of the amount of material in an object; a quantitative measure of inertia

NEWTON’S THREE LAWS Acceleration: the rate of change of velocity with time Weight: weight is a force caused by the gravitational field of the Earth (or other celestial object).

NEWTON’S THREE LAWS TYPES OF FORCES ContactNon-Contact SurfaceGravitation TensionElectrostatic (Compression)Magnetic VariableStrong force

NEWTON’S THREE LAWS Surface Forces Tension Forces Variable Force Friction Normal Strings Wires Springs Compression Forces Normal

NEWTON’S THREE LAWS NEW UNIT!  F = ma 1.0 Newton = 1.0 (kg)(m/s 2 )

NEWTON’S THREE LAWS This means N/kg is equivalent to m/s 2. Expressing it as N/kg shows that it is a “force field” (1 Newton of force for every kilogram of mass).

NEWTON’S THREE LAWS Example: Since weight is a force, we can use Newton’s 2 nd Law for an 80 kg person:  F = ma  F = (80 kg)(g)  F = (80 kg)(9.8 N/kg) = 784 Newtons

NEWTON’S THREE LAWS Useful Conversions: 1.00 lb= Newtons lbs= 1.00 Newton 2.2 lbs= 1.00 kg Since there are lbs per Newton, this works out to 176 lbs.

NEWTON’S THREE LAWS Men In Black 3 – A not too bad view of gravity on the Moon – except for the voice thing at the end…

NEWTON’S THREE LAWS Movie: John Carter of Mars - Note how much he moves on Mars – less than the Moon; although the movie exaggerates this later on…

NEWTON’S THREE LAWS Newton's 3 rd Law: the Law of Interaction: For every action there is an equal and opposite reaction.

NEWTON’S THREE LAWS KEY POINTS: 1. Forces always occur in pairs. 2. You cannot exert a force on an object without the object exerting the same force back on you.

NEWTON’S THREE LAWS In rockets, the hot gases in the combustion chamber press against all sides equally. The pop bottle acts as the combustion chamber. The pressure on the opposite side of the combustion chamber is now unbalanced and pushes the rocket.