GRAVITY, MAGNETISM, AND ELECTRICITY UNIT FORCES AND INTERACTIONS.

GRAVIT

Y, M

AGNETISM,

AND ELE

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UNIT

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GRAVIT

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GRAVITY

A plane falls from the sky, an apple falls from the tree these events take place because gravity.

Gravity is a force that pulls objects toward each other.

Issac Newton concluded that a force acts to pull objects straight toward the center of the earth.

UNIVERSAL GRAVITATION

Newton realized that gravity acts everywhere in the universe, not just on Earth.

It is the force that keeps all the planets in our solar system orbiting around the sun.

UNIVERSAL GRAVITATION

The law of universal gravitation state that the force of gravity acts between all objects in the universe.

This means that any two objects in the universe, without exception attract each other.

FACTORS AFFECTING GRAVITY

Two factors affect the gravitational attraction between objects: mass and distance

Mass is a measure of the amount of matter in an object. Mass is measured in kilograms

FACTORS AFFECTING GRAVITY

The more mass an object has, the greater its gravitational force.

In addition to mass, gravitational force depends on the distance between the objects. The farther apart two objects are, the lesser the gravitational force.

WEIGHT AND MASS

Mass is the measure of the amount of matter in an object

Weight is the amount of gravitational force exerted on an object

DON’T GET THESE TWO CONFUSED!!!!!!!!!!!

WEIGHT AND MASS

The force of gravity on a person or object at the surface of a planet is known as weight

Weight varies with the strength of the gravitational force but mass does not.

Astronaut in Space

Weight on Moon 270 N

Weight on Earth 1,617 N

Mass on Moon 165 kg

Mass on Earth 165 kg

GRAVITY AND MOTION

When you hold a book, you exert a force that balances the force of gravity.

When you let go of the book, gravity becomes an unbalanced force and the book falls

FREE FALL

When the only force acting on an object is gravity, the object is said to be in free fall.

Objects in free fall is accelerating

In free fall the forces of gravity is an unbalanced force, which causes an object to accelerate.

FREE FALL

FREE FALL

Near the surface of the earth the acceleration due to gravity is 9.8 m/s²

This means that for every second an object is falling, its velocity increases by 9.8 m/s

In the absence of air, two objects with different masses fall at exactly the same rate.

AIR RESISTANCE

Theoretically, all objects are supposed to fall at the same rate but we know that this is not always the case.

Objects falling through air experiences a type of fluid friction called air resistance

Friction is the direct opposite to motion, so air resistance is an upward force exerted on falling objects

Not all objects have the same air resistance

Objects with more surface area has more air resistance

AIR RESISTANCE

Air resistance increases with velocity, or speed in a given direction.

As the object falling speeds up, the force of air resistance increases

At one point, an object falling will fall fast enough that the upward force of air resistance becomes equal to the downward force of gravity on the object.

AIR RESISTANCE

The object continues to fall, but its velocity remains constant.

The greatest velocity a falling object reaches is called its terminal velocity

Force of air resistance = weight of the object

INTR

ODUCTION T

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ELECTR

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https://www.brainpop.com/technology/energytechnology/electricity

/

ELECTRICITY

e- movement

negatively charged area positively charged area

The movement of electrons from one place to another

ATOMS AND CHARGE

All matter is composed of small particles called atoms

Atoms are composed of even smaller particles called protons, neutrons, and electrons

Electrons = negative charge

Protons = positive charge

Neutrons = no charge

CHARGES CAN EXERT FORCES

A charge is a physical property that describes how charged objects interact with one another.

A charge exerts a force----a push or a pull

There are two types of charges Positive Negative

Forces depend on weather the forces are the same type or opposite

CHARGES CAN EXERT FORCES

The law of electric charges states that like charges repel and opposite charges attract

THE ELECTRIC FORCE AND THE ELECTRIC FIELD The force between charged objects is an electric force

The strength of the electric force is determined by two factors: Size of the charges –greater the charge the greater the force Distance –closer together the charges are the greater the force

THE ELECTRIC FORCE AND THE ELECTRIC FIELD The electric force exists because charged particles have

electric fields around them.

An electric field is a region around a charged particle that can exert a force on another charged particle.

ELECTRIC FIELDS

Electrical field

two charges are separated

vectors (lines of force) point towards negative charges and away from positive charges

strength of field (magnitude)= distance between two charges

closer particles = stronger field

A force field that fills the space around electrical charges

STATIC ELECTRICITY

e- displaced & builds charge(not moving through a conductor)

Eventually electrons “jump” to a positively charged object

Examples

Plastic sheet & hair

Walking on carpet &

Touching a metal doorknob

Electrons are displaced WITHOUT moving througha conductor

MAGNETS A

ND

MAGNETISM

https://www.brainpop.com/science/motionsforcesandtime/magnetism

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MAGNETS

Elements that can be magnetic

1. Fe: Ironsoft iron loses magnetism easily

2. Co: Cobaltused to harden tools

3. Ni: Nickelused to make jewelry

Other magnets:

4. Compass

5. Earth

Materials whose atoms can be aligned

PROPERTIES OF MAGNETS

Any material that attracts iron, nickel, or cobalt is called a magnet.

All magnets have the following properties: Two poles Create a magnetic field Exert force

The parts of the magnet where the magnetic effects are the strongest are called the poles

If you attach a string to a magnet and let it hang there is one end that will always point itself to the north.

The part of the magnet that orients itself north is called the north pole of the magnet

The part of the magnet that orients itself south is called the south pole of the magnet

MAGNETIC POLES

The force of repulsion or attraction between the poles of magnets is called the magnetic force.

The magnetic force between magnets depend on how the magnets line up

MAGNETIC FORCES

A magnetic field exists in the region around a magnet in which magnetic forces can act.

MAGNETIC FIELDS

MAGNETIC FIELDS

Magnetic field lines

1. Leaves north pole & enters south pole

2. Lines closer together = stronger field

NOTICE

3. Strongest at the poles

4. Field lines start at the NORTH pole and travel towards the SOUTH pole

An area where the force exists; area where force is felt

WHAT MAKES A MATERIAL MAGNETIC?

ATOMS AND DOMAINS

All matter is made of atoms with moving electrons.

Moving electrons create a magnetic field.

In metal objects atoms are grouped together in tiny regions called domains

The arrangement of the domains in an object determines whether the object is magnetic

EARTH AS A MAGNET

Recall that if a magnet is allowed to hang freely it will point to the north .

In fact, every time you use a compass you take advantage of this property, because a compass contains a freely rotating magnet.

The real question is why do magnets point north?

In 1600 an English scientist named William Gilbert suggested that magnets point to the north because Earth itself is one giant magnet.

Each does behave as if it has a bar magnet running through its core.

ONE GIANT MAGNET

Why does the needle of a compass point north?

The magnetic pole of Earth that is closest to the geographic north pole is actually the magnetic south pole.

NORTH IS SOUTH

THE CORE OF THE MATTER

Scientists think that the Earth’s magnetic field is produced by the movement of electrons in the Earth’s core.

The inner core is a solid iron and nickel

The outer core is liquid metal because there is less pressure.

As earth rotates the liquid in the core flows and causes electric charges to move creating a magnetic field.

A MAGNETIC LIGHT SHOW One of the most spectacular effects caused by the Earth’s magnetic fields is

a curtain of light called and aurora.

An aurora is formed when charged particles from the sun interact gases in the atmosphere.

When the charged particles hit the gases they emit light.

Earth’s magnetic fields at like a barrier so you really only see an aurora near the north and the south pole

The lights seen near the northern magnetic pole is called aurora borealis or the northern lights

https://www.youtube.com/watch?v=ZxyT26Lg55Q

MAGNETISM F

ROM

ELECTR

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THE DISCOVERY OF ELECTROMAGNETISM

In 1820 Danish scientist Hans Christian Oersted discovered the relationship between electricity and magnetism.

Oersted concluded that an electric current produces a magnetic field

The direction of the magnetic field depends on the direction of the current.

Electromagnetism is the interaction between electricity and magnetism

ELECTRICITY MAGNETISM

How can you tell?Compass needle moves when near electrical current - creating an magnetic field

Electric currents cause magnetism

ELECTROMAGNET

Electromagnetisma moving charge (electricity) produces a magnetic field

More coils of wire= more current = stronger magnet

Bigger battery = stronger magnet

A magnet with a field produced by an electric current

ELECTROMAGNETIC INDUCTION

1831 – Michael Faraday (England) and Joseph Henry (US) independently discovered that electric current could be produced by moving a magnet in and out of a coil wire

ELECTROMAGNETIC INDUCTION

https://www.brainpop.com/technology/energytechnology/electromagneticinduction/preview.weml

MAGNETISM ELECTRICITY

How can you tell?

Electromagnetic induction

moving a magnet in and out of a coiled wire created an electrical current without a battery

Moving magnet can generate electricity

• Both can cause each other

• Likes repel

• Opposites attract

SUMMARY OF E & M

ELECTRICITY

Can be + or -

Can flow (current)

Can jump (static)

E = Electricity and M = Magnetism are related!!

MAGNETISM

► Can NOT have only 1 pole

► Can be Normal (N) or Reversed (S) pole

► Can move through field

► Causes sun spots, flares, CME