Grade 8: Forces between and not touching

Big Idea: Forces between objects act when the objects are__________

in direct contact and when they are not touching.

field

area around any object in which forces can act without touching

gravity

force of attraction between objects that is due to their masses;

magnet

any material that attracts iron or materials containing iron

electromagnetism

the interaction between electricity and magnetism

electromagnet

solenoid with a soft iron core inside

Gravitational force increases as ________________ increases.

mass

Gravitational force decreases as ___________________ increases.

distance

electromagnetic induction

process of creating a current by changing a magnetic field

2 components of projectile motion

horizontal movement and vertical movement

terminal velocity

the constant velocity of a falling object when the force of gravity is balanced by the force of air resistance

electric force

the force between two charged objects

electric field

a region around a charged object where a force is exerted on other objects

electric generator

a device that converts mechanical energy into electrical energy through electromagnetic induction

electric motor

a device that converts electrical energy into mechanical energy

magnetic poles

ends of a magnet that have opposing magnetic qualities

free fall

when the only force acting on an object is gravity such as in a vacuum or space

static electricity

A buildup of charges on an object (clothes from a dryer; comb or balloon on hair)

3 ways an object can become charged

friction, conduction, induction

charging by friction

two objects rub together and one becomes positively charged and the other becomes negatively charged (cloth on glass rod, hair on balloon)

charging by induction

the rearrangement of electrons on an uncharged object caused by a nearby charged object

charging by conduction (contact)

Transfer of charge between objects by allowing them to come into contact with one another

solenoid

A coil of wire that produces a magnetic field when carrying an electric current

How can magnetic field of a solenoid or electromagnet be increased?

1. increasing the number of loops in the coil

2. increasing the electric current in the wire

electromagnet

a coil that has a soft iron core and that acts as a magnet when an electric current is in the coil

Properties of magnets

1. Magnets attract objects of iron, cobalt and nickel.

2. Whether a material is magnetic or not depends on the material's atoms.

2. The force of attraction of a magnet is greater at its poles than in the middle.

3. Like magnetic poles repel each other.

4. Opposite magnetic poles attract each other.

magnetic field

The area of magnetic force around a magnet

Earth's Geographic and Magnetic Poles

1. Earth acts like a giant magnet.

2. Earth has a magnetic field.

3. Compass needles and north poles of magnets point to Earth's magnetic south pole which is near Earth's geographic north pole.

How does lightning form?

Friction in the clouds creates charges.

Induction from the cloud creates a charge in the ground.

The charges are released through a static discharge event as the electrons are conducted to the other parts of the cloud/ground.

What has to happen for a feather and a bowling ball to fall at the same rate?

There would have to be no air resistance for them to fall at the same acceleration.