Physics middle school

How is position measured

Meters

How is mass measured

Kg

How is velocity measured

meters per second (m/s)

What is a reference frame

The point of view that you observe and measure things from

Used to help define the motion or position of an object

What is the standard reference frame

Earth’s surfac

More force equals

More acceleration

More mass equals

Less acceleration

Equation for force mass and acceleration

F = M x A

What is net force

Sum of all forces acting upon an object

What are newton’s 3 laws?

For every force there is an equal and opposite reaction force. 

An object at motion/at rest will remain in motion/at rest unless acted upon by another force (inertia)

F = M x A

Properties of gravitational forces

Attractive forces

Exists between all objects with mass

Depends on mass of objects and the distance between them

More mass = More force

More distance = Less force

Properties of electric forces

Non-contact force

Caused by charge (most things are neutral)

More charge = More force

More distance = Less force

Properties of magnetic forces

Non-contact force

Attract and repel (N vs S)

More magnet quality = More force

More distance = Less Force

Properties of field forces:

Includes non-contact forces (electric, magnetic, gravitational)

Electric effects charged objects

Magnetic effects magnets

Gravitational effects objects with mass

Fields extend through space and influence other objects located within them.

Magnitude depends on strength of the field and distance from the source.

Direction of the force follows the lines of the field.

Electromagnetism

Electrical magnets

Temporary magnets in the presence of electricity

Higher current = More strength

More dense = Higher strength (spiral shaped = more strength)

Can change poles by changing the direction of the current

Can be turned on/off

A changing magnetic field can produce electricity (electromagnetic induction)

Properties of kinetic energy

Any object in motion has kinetic energy

More speed = more KE (more important)

Less mass = less KE

KE = (M x Vsquared) ½ measured in joules

Potential energy:

Potential energy is the stored energy an object has because of its position or condition.

Gravitational potential energy is relative to an items position on earth

Elastic potential energy has inside forces that try return to its original shape

Electric potential energy is based on charges

Magnet potential energy is based on poles

Energy cannot be created or destroyed…

Only changed from one form to another

Wave terms:

Wave

Period

Wavelength

Frequency

Speed

ergo, wave speed

Amplitude

Wave: A disturbance that can propagate

Transfers energy without transferring matter

Period: Measured in seconds (s), time it takes for a wave cycle to complete

Wavelength: Measured in meters (m), distance between identical points of adjacent waves

Frequency: Waves per second

Speed: Distance/time

So wave speed = wavelength / frequency (m/s), Wave type and medium in which it travels through effects the waves speed

Amplitude: Maximum change from the equilibrium

Mechanical waves

NEED a medium to travel through,

eg. sound needs air, but light doesn’t need a medium.

Transmission

When a wave passes from one material into another one

Eg. Sun → Space → Atmosphere → Sunglasses → Eyes

Depends on the wavelength and material. This changes how much and what is transmitted, eg. sunglasses block UV light and blue light

Refraction

Refraction occurs when a wave’s path bends at a boundary as it enters a new medium

Eg. For light waves, higher frequencies bend more than lower ones when passing through a medium like glass

Reflection:

A wave bounces off of a boundary between two materials

Depends on type of wave, wave frequency and material

Absorption:

When a wave loses energy as it transmits into a material

Can happen in a medium, or at the boundary between two materials

When a wave is absorbed, the energy is transformed to another form of energy

Depends on type of wave, wave frequency and material

Analog vs Digital

Analog: Any value within a given range

Digital: A value represented by a number of discreet or separate levels

Analog: Can display anything

Digital: Can only display certain values