physics forces

The effects forces have on objects

• when a force is put on an object, Something about this object may change

• Forces can change the shape beat and direction of an object.

What is a force?

• A push or pull on an object

How do you measure a force?

In Newtons using a newton balance/ spring balance

What is a newton balance?

Measures the size of the pulling force .

Why do objects fall when dropped?

Gravity

What is weight?

Weight is a force and is the earths pull on an object.

What do you usually have to do in order to make a spring stretch?

Apply force

What does gravity do?

It pulls objects down towards the centre of the Earth.

Weight and mass are the same?

False, they are not the same

What is weight?

The force of Gravity acting on an object- measured in newtons.

What is mass?

The measure of the amount of mass in an object- measured in kg

Is gravity the same for all objects?

Yes

The bigger the mass…

The bigger the weight

Weight equation

Mass x 10

Gravity equation

Weight divided by mass

Mass equation

Weight divided by 10

How is weight measured?

Newtons

Gravity measured?

N/ kg

Mass measured?

Kg

What is the force of gravity on the moon compared to earth?

The moons force of gravity is smaller than.

What is gravitational field strength?

The region around the Earth in which a mass experiences a force due to the pull of the earths gravity.

Weight divided by mass equals what?

Gravitational field strength (g)

The mass of an object always what?

Stays the same

can weight change of an object?

Yes. If it moves planets

If the force doubles what happens to the extension?

It also doubles.

What happens when electrical charges Flow in a wire?

A magnetic field is formed

What shape do magnetic field lines form around the wire?

A cylinder

What happens when the current stops flowing?

The magnetic field disappears

How can you increase the strength of the magnetic field?

By coiling the wire to form a coil (solenoid)

What does more coils equal?

A stronger magnetic field

What is hookes law?

The theory that the extension of the spring is directly proportional to the applied force

What is the Elastic limit?

It’s the max force applied to the spring, So it will return to its original length when the force is removed. Beyond elastic limit = The spring is permanently deformed and no longer obeys hookes law.

Magnetic materials and magnetic elements=

• paper clips

• Steel coin

• Iron

• Nickel

• Cobalt

What is an alloy?

A mix of two or more elements : Brass( Copper+ Zinc)

What is a compound?

Two or more elements chemically react with each other : salt ( sodium + chloride)

What do iron alloys do?

Attract

What do iron compounds do?

They repel

What is a bar magnet?

Rectangular shaped magnet, with a pole on each end.

Poles?

North and south poles.

North Pole colour?

Red

what poles attract and repel?

Like poles repel, unlike poles attract

What are magnetic fields?

• region around a magnet with the magnetic effect.

• Compasses can show the magnetic field lines

Magnetic field patterns?

• directed from North to South

• Start and finish on a magnetic pole

• The closer the field lines, the stronger the field.

Explain the magnetic and geographic poles.

Since the North Pole of a magnet points geographically north the magnetic south must also be at the geographical north.

Making a compass

• when a bar magnet is hung, so it’s free to rotate, it lines up north/ south and always points north.

• The end that points north = “ north seeking pole” and the other is “ South seeking pole “

The Earth’s magnetic field

Strongest at poles and weakest near equator

What is electromagnetism?

• can be turned off and on

• Discovered in 1812 by Hans Christian Oersted. He held a small compass near a wine wick that had a current flowing through it

How do you make an electromagnet?

• put a soft iron core inside the solenoid, The strength of the magnetic field is stronger.

Can a nonmetal material be turned into a magnet by a magnetic field?

No.

Factors that would affect the strength of an electromagnet?

• Number of coils( increase)

• Size of current ( Increase)

• Strength of magnetic core

How to measure strength?

Attach masses ( kg) To the magnet and see how much it can hold.

What are superconducting magnets?

• Electromagnet built Using superconducting coils.

• Need to be cooled to a very low temperature using liquid helium.

• Stronger magnetic field than normal electromagnets.

Forces may what to an object speed?

Increase or decrease

What is friction?

• Force made When surfaces rub together to try to slide over each other. No surface is perfectly smooth.

• When surfaces slide together tiny high points on one surface will catch on the other causing friction.

What does fraction always do to relative motion?

Opposes it.

What does friction do?

Generates heat and causes wear and tear.

You can reduce friction by doing what?

Stream lining. It’s a design process to make cars go through the air smoothly.

Friction can also occur…

Between objects, liquid and gas.

Fraction forces can occur…

Due to the flow of water around a high-speed boat.

Air resistance=

Movement of air over surface causes air friction.

Bigger surface area=

Bigger air resistance

Bigger speed =

Bigger air resistance

What are maglev trains?

• maglev trains use magnetic levitation.

• They use powerful electromagnets to “float” The train over the track

• Reduces friction

• Streamlined