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 table 2. 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 peddle 3. 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 1 st Law Projectile motion -a thrown object into the air and the path that it follows 1. downward = gravity force 2. 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 shuttle The 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 object 2. 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 Massgravity Mg Kg9.8 m/s 2 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 effect you 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

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 liquid example 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 gravity If 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 1 st 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 formula T 2 = 4 x 9.86 (L/G) so T 2 = x (L/9.8) G = 9.8m/s 2 T = time of a full to and fro swing measure with stop watch while counting and divide by how many times it swung a full back and forth movement L = length of the string measure with a ruler in meters PI = 3.14, squared = 9.86 So let’s try to prove that gravity is 9.8m/s 2 G = T 2 divided by times the length of the string G = T 2 /39.44xL

ENERGY IN MOTION related to 2 nd Law Speed distance traveled time it took to travel that distance *distance / time = speed Meters / seconds Miles / 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 acceleration kg x m/s/s m x a = the force that produces movement *Force is measured in Newtons

Energy in Motion related to 3 rd Law Example of action, reaction -pool ball collision Mass x velocity = mass x velocity -helicopter –downward force of air equal 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 direction They are moving relative to each other in a parallel direction Their 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