Forces - a push or pull that acts on a object due to its interaction with other object

Forces are measured in Newtons (N)

For example: when your hands pushes a box it exerts a force of i.e: 5N

 Forces have magnitude and direction, e.g: the force is acting to the right (direction) 

This means that forces are classed as vector quantites (both m and d)

Contact force - means two objects are physically touching

The 4 contact forces you need to know: friction, air resistance, tension

The last one is called normal contact force or reaction force

Non contact force

Means that it doesn't require the 2 objects to be touching

Examples include: gravitational force, magnetic, electrostatic

Non contact forces we talk about them ascan also be called a 'field of influence' round a object because the forces can act on anything in that surrounding area.

For example gravity is a force or attraction between any two objects that have mass, like the Earh or people. We still feel this force of attraction though even if we are not on the Earth.

Magnetic forces and electrostatic forces

Can be attractive or repulsive

For all non contact forces - the strength of them will decrease as the objects get further apart 

Free Body Diagrams and how they can help you find the resultant force

A free body diagram is a diagram that show all the forces acting on an object. We show the forces using force arrows - we place them in different positions on the diagram.

The arrow that is going forwards is called the Thrust

The arrow that is going backwards is called Air resistance or drag

The arrow that is going downwards is called weight

The arrow that is going upwards is called lift

All forces are vectors: vectors have magnitude and direction

The magnitude comes from how long the arrow is, and we can label each of them in Newtons

How to figure out the resultant force:
You start with only the vertical component first -  both 80,000N 

80,000 - 80,000 = 0N

Then you focus on the horizontal component: 120,000N and 90,000N 

120,000 - 90,000 = 30,000N as the resulstant force

Different types of elasticity:

When you apply a force to an object you could cause it to be compressed, stretched or bend/bent. If we want to keep the object still we have to apply more than one force. Example: even if we squish something against the floor - so we only apply one force, the floor itself is applying a force upwards = 2 forces being applied.

Deformed

When an object changes shape we say it has been deformed. There are 2 types of deformation that you need to know: elastic and inelastic. 

If an object goes back to its original shape (e.g: a stretched spring) after the forces have been removed we call it elastic deformation because its able to spring back. However if the object doesn't quite return to its normal shape, and in some way stays deformed - its called inelastic deformation. 

(Continuing straight from the last card)

Extension

The extension is where the length of the spring is increased when its stretched. Example: if a spring is hanged from something solid, we can measure how the spring's length changes as we add a downwards force. The spring's own mass will be exerting its own force in the form of weight - because of this the natural length will be a bit shorter than the length itself because there will already be some extension.

2 types of waves: transverse and longitudinal

In longitudinal, the vibrations are parallel to the direction of wave travel. Examples of longitudinal waves are:

• sound waves
• ultrasound waves
• seismic P-waves

• In transverse, the vibrations are at right angles to the direction of wave travel. Examples: ripple of water, vibrations in a guitar string ,etc

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magnetism and electromagnetism

Magnetism and Electromagnetism

The bar magnets look like this: with a few lines around them and a rectangle bar around it

N               S            The lines always point to S. The lines are curvy

Solenoids

 a solenoid converts electrical energy into mechanical work.

waves part 2 

Longitudinal LEFT AND RIGHT

Transverse UP AND DOWN

Wave period and wave speed

The time period of a wave can be calculated using the equation:

time period = 1/frequency

This is when:

• time period (T) is measured in seconds (s)
• frequency (f) is measured in hertz (Hz)