physics

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waves facts

  • Frequency = waves per second 
  • Thay have a peak
  • The EM has different frequencies 
  • They have a trough 
  • Longitudinal waves = sound waves 
  • Transverse waves = microwaves 
  • Wavelength is the distance between peaks 
  • Period = the time taken for one whole wave cycle
  • Phase difference is the distance between two different wave's peaks 
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polarisation

Why does polarisation prove light is a transverse wave?

Polarisation proves light is a transverse wave because polarisation is the filter of ligth.You can polarise vertically or horizontally. If light was a longitudinal wave it would not be able to be polarised as it wouldn't travel through the polarizer 

What is polrisation?

Polarisation stops waves at cetain angles travelling through a polarizer. a ray of light looks like a normal transverse wave however it has man different angles to the plane. A polriser only lets certain angles in. For example only lets the horixontal wave through. This is how sun glasses work to protect your eyes

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material science definitions

Elastic - the ability to strecth and return to form 

Plastic - a material that has changed and cant return 

Strain - is the change in materials length 

Deformed - when the material has changed shap for the good

Stress - amount of force applied over an area

Dense - mass/volume

Force - the amount of push something needs to change its; velocity, direction, shape or acceleration

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Moments

  • Moments = force X distance 
  • A moment is the turning force around a pivot 
  • These are also known as the torque of a driven rotating object
  • Bridges have several moments that act in differnet direction when a load is placed upon them 
  • larger force of distance = larger  oment or turning effect 
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Mechanics

  • The centre of mass is the single point that its whole weight acts through 
  • The lower the centre of mass and wider the base the mire stable an object is 
  • When the line of action of an object's weight falls outside of its base, a resultant moment occurs, which provides a turning force (this causes it to topple)
  • if an object is being held by supports, each support wont always have the same upwards force
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Projectiles

How to answer a projectiles question 

  • Assume friction has no affect 
  • Assume lift is constant 
  • Assume drag is minimaln

What is a projectile?

A projectile is any moving object that has been propelled at a force for a shprt amount of time. For example a bullet in a gun or a person being shot out of a cannon.

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Newtons laws

Newtons 1st law

Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied.

Newtons 2nd law

The relationship between an objects mass, is acceleration and force applied. F=Ma. Acceleration and force are vectors, in this law the direction of the force vector is the same as the direction of the accelration vector.

Newtons 3rd law

For every action there is an equal and opposite reaction 

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Lift problems

  • If the lift is moving up, the force pulling up is higher than gravity
  • When the lift us going up and acclerating - T=mg + ma
  • When the lift is going down at constant velocity - T=mg
  • The lift is moving up but decelrating - T = mg + ma (T is negative)
  • The lift is acclerating downards - T= mg + ma
  • The lift is decleraing downwards - T = mg + ma
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Collisions

Before collision p = ma 

After collision p = (M+m)v

What we start off with has to be presented in the end of the collision. Therefore the momentum at the start will eual the momentum at the end

In a elastic collision, all energy is conserved and accounted for

Momentum is conserved in an explosion 

Before a staionary bomb explodes its momentum is zero. When it explodes the bomb fragments will skater. The vector sum of the momentum of all the fragment is zero. This is because they all cancel each other out. This menas the strat momentum = the end momentum

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