A. Newton’s Laws Sir Isaac Newton (1642–1727)  able to state rules that describe the effects of forces on the motion of objects I. The First 2 Laws of Motion

An object moving at a constant velocity keeps moving at that velocity unless an unbalanced net force acts on it (LAW OF INERTIA) B. The First Law of Motion

C. Inertia & Mass --inertia-- the tendency of an object to resist any change in its motion - If object is moving  it wants to keep moving - If object is at rest  it wants to stay at rest UNLESS…… …UNBALANCED forces act on it!

-The velocity of an object remains constant… UNLESS… …a force changes it!

-The inertia of an object is related to its mass The greater the mass of an object  the greater its inertia

-- mass -- the amount of matter an object has -- weight -- the amount of mass PLUS the force of gravity acting on an object Force is calculated using units of m/s² AND kg (or g)  these units combine into a unit called a NEWTON (mass + acceleration)

D. The Second Law of Motion The acceleration of an object is in the same direction as the net force on the object Newton's 2nd Law of Motion Demo

-Acceleration can be calculated from the following equation: 1.) Force & Acceleration Newton's Law's of Motion Song

Force = mass x acceleration - Another Maaaaagic Triiiiangle! (*oooohhh…aaaaahhhh*) UNIT USED for FORCE: NEWTONS (N)

REMEMBER: acceleration is the change in velocity divided by the time it takes for the change to occur  HINT: Now for problems you may have to solve for acceleration first before dividing the force!!!

2.) Mass & Acceleration -The acceleration of an object depends on its mass as well as the force exerted on it

- MASS vs. WEIGHT  An object’s WEIGHT (mass + force of gravity) may be different in different places in the universe because of different forces of gravity…Translation: WEIGHT CAN CHANGE!  An object will always have the same MASS (amount of matter) no matter where that object is….Translation: MASS STAYS THE SAME!

Bill Nye: Mass vs. Weight & Momentum

II. Gravity A. What is Gravity? -- gravity -- attractive force between any 2 objects  depends on the masses of the objects & the distance between them

Increasing mass increases an objects gravitational force ! Decreasing distance between objects increases gravitational force!

1.) Gravity- A Basic Force The “Big 4” Basic Forces: GRAVITY ELECTROMAGNETIC FORCE STRONG NUCLEAR FORCE WEAK NUCLEAR FORCE

B. Law of Universal Gravitation G  universal gravitational constant d  distance between two masses m1 & m2  the two masses

TRANSLATION:  Law of Universal Gravitation enables the force of gravity to be calculated between any 2 objects if their masses & the distance between them is known

1.) Range of Gravity - No matter how far apart 2 objects are, the gravitational force between them never completely goes to zero  gravity is a LONG-RANGE FORCE Nye Tunes "G-R-A-V-I-T-Y"

C. Earth’s Gravitational Acceleration - When all forces except gravity acting on a falling object can be ignored, the object is said to be in free fall -Close to Earth’s surface, the acceleration of a falling object in free fall is about 9.8 m/s 2

- Symbol for acceleration of gravity  g -By Newton’s 2 nd law of motion  force of Earth’s gravity on a falling object = object’s mass times the acceleration of gravity… F = m x g UNIT USED = NEWTONS (N)

1.) Weight ***Weight is a force *** ***Mass is a measure of the amount of matter an object contains***

D. Weightlessness & Free Fall 1.) Floating in Space - If gravitational forces never disappear  how does one become “weightless” (example: astronauts in space)?

Objects will seem to float because they are all falling with the same acceleration  astronaut & ship are falling towards Earth but falling at the SAME RATE Fun in Space- Zero Gravity - NASA footage

E. Projectile Motion - Earth’s gravity causes projectiles to follow a curved path

1.) Horizontal & Vertical Motion -When you throw a ball  force exerted pushes the ball forward to give it HORIZONTAL MOTION

-Horizontal Velocity of ball is constant (*ignoring air resistance*) -When you let go of the ball, gravity pulls it downward  giving it VERTICAL MOTION  ball travels in a curve

2.) Horizontal & Vertical Distance -If a ball as thrown in a perfectly horizontal direction, would it take longer to reach the ground than a dropped a ball from the same height? NO!!! They would drop at the same time! Projectile Motion

-Both balls travel the same vertical distance in the same amount of time  thrown ball travels a longer horizontal distance

F. Centripetal Force - When a ball enters a curve it is accelerating because its direction is changing (even if its speed does not change) Centripetal Force demo

-When a ball goes around a curve  change in the direction of the velocity is toward the center of the curve

--centripetal acceleration-- acceleration toward the center of a curved or circular path --centripetal force-- net force exerted toward the center of a curved path

1.) Centripetal Force & Traction -A car rounds a curve on a highway  centripetal force acts on the car to keep it moving in a curved path

 Centripetal Force is the frictional force (traction) between the tires & road surface

III. Newton’s Third Law When one object exerts a force on a second object  the second one exerts a force on the first that is equal in strength & opposite in direction Bill Nye & Newton's 3rd Law

A. Action & Reaction - When a force is applied in nature  a reaction force occurs at the same time

-Even though the forces are equal, they are not balanced because they act on different objects EXAMPLE: A swimmer “acts” on the water, the “reaction” of the water pushes the swimmer forward  a net force, or unbalanced force, acts on the swimmer so a change in their motion occurs Action and Reaction

B. Momentum --momentum-- a product of mass & velocity - Momentum symbol  p - Unit for momentum  kg · m/s

1.) Force & Changing Momentum -By combining acceleration equation & force equation  Newton’s 2 nd Law Equation: ***Final Momentum  mv f ***Initial Momentum  mv i

C. Law of Conservation of Momentum -Momentum of an object doesn’t change…. …UNLESS …its mass, velocity, or both change! Newton's Cradle

-Momentum can be transferred from one object to another!

Law of Conservation of Momentum: If a group of objects exerts forces only on each other  their total momentum doesn’t change

1.) When Objects Collide - Results of a collision depend on the momentum of each object

- When an object hits another from behind  momentum occurs in the SAME direction

- When an object hits another head on with the same force  momentum is ZERO - If one object hits another head on with the more/less force  momentum is TRANSFERRED