Wile E. Coyote

If Wile E. Coyote and a bolder fall off a cliff at the same time which do you think will hit the ground first?

Objects fall to the ground at same rate› Acceleration due to gravity = same for all

objects All objects accelerate toward earth at a

rate of 9.8 meters per second› 9.8 m/s/s

Using the figure pg 37Math Break pg 37

What is more affected by air resistance a school bus or a race car?

Fluid friction opposes motion of objects› Also known as air resistance

Amount of air resistance depends on:› Size of object› Shape of object

Self Check

Figure 3

Net force does not equal 0 = object accelerates downward

Air resistance increases as speed of object increases

Upward force of air resistance increases until it exactly matches the downward force of gravity

This causes net force of 0= Terminal Velocity (Constant Velocity)

Pg 38 Figure 4

Simulation: galileo_pisa_finalv1.2

Free Fall= No air resistance

Free fall can only happen where there is no air› In a vacuum› In space

Pg 39 Figure 5

What problem might you have if you were to sky dive on the moon?

Orbiting objects are in free fall

An orbiting object is going forward and falling- It is falling around the earth

Pg 40 Using the figure Figure 7

›

Projectile Motion

The curved path an object follows when thrown

Thrown objects and falling objects have the same acceleration

Orbiting objects are examples of projectiles

Projectile objects have two components- horizontal and vertical

Both components are independent of each other

“An object at rest remains at rest and an object in motion

remains in motion at constant speed and in a

straight line unless acted on by an unbalanced force”

Part 1: Objects at Rest› Object will not move until a push or pull is

exerted on them Ex. Plane won’t fly unless pushed by exhaust

from engine

Part 2: Object in Motion› Object will move forever at the same

speed and in same direction unless some unbalanced force acts on it Ex. Bumper car stops but you continue to

move forward until your seat belt stops you

Pg 44 Apply

Friction: Makes it difficult to observance of the first law on everyday objects› Ex. Grass causes a rolling ball to stop

Inertia: Tendency of all objects to resist any change in motion› Ex. Slide toward side of car when driver

makes a sharp turn Mass: Smaller mass has less inertia

than object with large mass› Ex. Push car vs. bike

Pg 45 Self Check

“The acceleration of an object depends on the

mass of the object and the amount of forced applied”

Part 1: Acceleration Depends on Mass› Same force= objects acceleration

decreases as its mass increases and its acceleration increases as its mass decreases Ex. Shopping Cart

Part 2: Accelerating Depends on Force› An objects acceleration:

Increases as force increases Decreases as force decreases

a= F/m F= m X a

M= F/a

Math Break Pg 47

“ Whenever one object exerts a force on a second object, the second object

exerts an equal and opposite force on the

first.”

All forces act in pairs: Actions and Reactions

Can occur when there is no motion› Ex: Action Force= Body exert force on chair Reaction force= force exerted by

the chair that pushed up on your body› No movement

Force Pairs Do Not Act on the Same Object› Ex. Swimming

Action force = exerted on the water by swimmer’s hands and feet

Reaction force = exerted on the swimmer’s hands and feet by water

The Effect of a Reaction Can be Hard to See› The force of gravity between Earth and a

falling object is a force pair› Pg 49 examples› Pg 49 real world connections

Momentum= Property of a moving object that depends on the object’s mass and velocity

P= m X v› P= Momentum› m=mass› V=velocity

More momentum= harder to stop or change direction

Law of Conservation of Momentum:› Two or more objects interact, may

exchange momentum, but total amount stays the same

› Ex. Billiards or Bowling Momentum and Newton’s 3rd Law

› Action force= billiard ball moves› Reaction force= stops cue ball’s motion