NEWTON’S THREE LAWS OF MOTION

I. An object will remain at rest or will continue to move uniformly in a straight line at a constant velocity (speed and direction) unless acted upon by a force.

Inertia example pushing a stationary object on a table2. The rate of change of velocity of an object is proportional

to the force acting on it(more input energy to an object = more velocity

Acceleration example stepping harder on a gas peddle3. If one object exerts a force eon another, that second

object exerts an equal and opposite force on the first

Action, Reaction

Energy in Motion related to 1st Law

• Projectile motion-a thrown object into the air and the path that it follows1. downward = gravity force2. forward = inertia force–an object will remain in its present state of rest or motion if no other force is introduced to it to cause a change (wants to keep doing whatever it is doing at the present time).-the motion always resembles a curved path

-gravity force is always stronger than inertia and the object is eventually pulled to the ground.

-example –a thrown ball

• Orbital motion-a path around an object is an orbit-an object following this path is in orbital motion-if an object’s forward force is inertia (its present speed) = the force of gravity (downward), then the forces are balanced and the object follows an orbital path.

-vertical force acting on the object is gravity– horizontal force acting on the object is inertia

(speed of the object)– + =

-example -space shuttleThe gravity force = the speed of inertia so it stays in

orbit-considered to be in freefall around the earth-anyone inside has a weightless experience

-if either force is increased or decreased

-increased gravity = falls to the ground

-increased inertia (speed) = escape velocity –can escape from its orbit

Newton's Universal Gravitational Law

• All objects are attracted to each other by the force of gravity

• Magnitude of the force depends on 1. the mass of the object2. the distance between objects

*increased mass = increased effect of the force of gravity on the object (takes more effort to pull down a larger object)

*distance increases between objects = decrease in the effect of the force of gravity on the object

Weight

• Weight = mass x acceleration force of gravity

Mass gravity

M g

Kg 9.8 m/s2

m x g = A Newton

mg = N

• Smaller mass = smaller gravitational force acting on the object

• Increased distance (farther apart) = smaller gravitational force acting on the objects

• Farther from the center of the earth (where gravity is thought to come from) --liquid core/plates moving– means smaller gravitational force acting on the object

• At sea level = greater gravitational effect on an object• On a mountain = less of a gravitational effect on an

object• On the moon = much less of an effect of earth’s

gravitational effectyou seem weightless because you only have

mass (m) not (mg) -g (gravity from the earth) is missing. Too far from the center of the earth for it to affect you. Plus

you have a small mass compared to the moon and the earth.

• Near the earth, the acceleration due to gravity is 9.8 m/s2

• For every second an object falls, its velocity increases 9.8 m/s every second

• 1sec 2sec 3sec

9.8m/s 19.6m/s 29.4m/s

+9.8 +9.8

Fluid Motion Energy

Viscosity

-the ease of difficulty to flow

-thin and nonsticky -water = easy to flow

-thick and sticky –syrup = difficult to flow

-friction force reduces the ease to flow

-high viscosity = greater resistance to flow turbulent flow

-low viscosity = not so much resistance to flow streamline flow

Fluid flow-the ease by which a fluid flows depending on its thickness and stickiness-fluid is described as air, a gas, or a liquidexample

air flow -a car moving through air –aerodynamics

gas flow -taking the top off a pop can -diffusion

liquid flow-pouring a liquid into a glass -measured in a substance’s internal friction which creates a resistance to flow

Ouch!

Example -raindrops in the atmosphere inside friction slows them down. This friction inside cancels out the acceleration due to gravityIf it didn’t, raindrops would hit the ground and your head at 150 m/s

Example-water pipe –faucet

-increase the pressure = turbulent flow-decrease the pressure = streamline flow

Air resistance

• Is a force that affects free falling objects• A feather is more affected than a boulder• Paper is more affected than a rock• As an object falls, if the air resistance

equals the pull down of gravity, the object appears to float. If there is no more acceleration of the object because the pull down = the upward force, the object is said to have terminal velocity

FREE FALL ACCELERATION

• All objects accelerate at the same rate towards the ground regardless of their masses

• A boulder and a pebble were thrown off of the Empire State building. If there were no other forces acting on them, they would hit the ground at the same time but with different forces

• The rate of the fall is the acceleration rate of gravity

• The gravity force acting between an object and the earth causes this acceleration of falling objects headed towards the earth

Harmonic Motion Energy

Harmonic motion related to 1st Law-a small to-and-fro movement that occurs whenever an apparent stationary object is slightly disturbed -pushed example pendulum-measured by lengths of the pendulum, the force of gravity, time of a full swing, and constants

Tries to keep going -Inertia but stops –gravity force

Pendulum Lab formula (get ready for this)

Check out length and weight of a pendulum to see if it affects the

time of its swing

Pendulum formulaT2 = 4 x 9.86 (L/G) soT2 = 39.44 x (L/9.8)

G = 9.8m/s2

T = time of a full to and fro swingmeasure with stop watch while counting and divide by how many times it swung a full back and forth movement

L = length of the stringmeasure with a ruler in meters

PI = 3.14, squared = 9.86

So let’s try to prove that gravity is 9.8m/s2

G = T2 divided by 39.44 times the length of the stringG = T2/39.44xL

ENERGY IN MOTION related to 2nd Law

• Speeddistance traveledtime it took to travel that distance

*distance / time = speedMeters / secondsMiles / hours

• Acceleration

to move with constant increasing speed

could be positive or negative acceleration

*speeding up = positive

*slowing down = negative

Force of Friction causes objects to slow down

Forces that affect a Moving cart

If the cart is moving, it wants to keep moving

Friction force

Gravity force

Force of the Pavement

Force of Inertia

FORCE = mass x acceleration

• There needs to be a applied strong enough to start an object rolling push or pull

• It must be an unbalanced force (stronger to overcome what the object is currently doing)

• Heavier things require more effort to start them rolling

• Mass x accelerationkg x m/s/sm x a = the force that produces movement

*Force is measured in Newtons

Energy in Motion related to 3rd Law

Example of action, reaction-pool ball collision

Mass x velocity = mass x velocity

-helicopter –downward force of airequal and opposite reaction =lift off-you sitting in a chair –downward force pulling you onto to the chair and opposite reaction = chair pushing up on you

• Relativity of motion– 1. relating one object’s motion to another

object’s motion– A car moves relative to the earth’s motion

-rotate, revolve– Example

Earth

• Example• A + B = relative velocity• ______A__________________________ - - -

- - - - - - - - - - - - - - - - - -• ________________B________________A car moving parallel to another in the same

directionThey are moving relative to each other in a parallel

directionTheir velocity (speed) determines their relative

velocity to each other

• A –B = Relative velocity

_______A___________________________

- - - - - - - - - - - - - - - - - - - - - -

____________________B______________

Comparison of A’s relative velocity to B’s relative velocity going in opposite directions

B – A = relative velocity