Physics

Energy

Cannot be created or destroyed

Net energy charge (in a closed system) is 0

Energy stores in a stretched bow string

Elastic potential

Energy stores in a flying arrow

Kinetic

Energy stores in a coal/battery/rocket fuel

Chemical

Energy stores in a pot of hot water

Internal

Energy stores in a rocket up high

Gravitational energy potential

Gravitational potential energy equation

Ep = mgh

Mass x gravitational field strengh x height

Kinetic energy equation

Ek = ½ mv²

½ mass x speed²

Power

Rate of energy transfer

Efficiency

Fraction of energy that goes in

What are energy sources

Oil, nuclear, wind, geothermal, solar, coal, hydroelectric, natural gas

Resistance of a wire (rp)

1. Measure lengh of the wire (ruler)

2. Turn on powerpack/ close switch

3. Read current off ammeter + potentional difference (voltmeter)

4. Calculate resistance using v = ir (r=v/i)

5. Let wire cool down (hot = higher resistance)

6. Repeat with different lengths

Resistance of a wire (rp) safety

The hot wire can give you a shock (turn off power and let cool before you move the crocodile clips)

Current, potential difference and total resistance of a series

Current = same everywhere

Potential difference = shared across components

Total resistance = can be added together

Current, potential difference and total resistance of a parallell circuit

Current = splits up and rejoins

Potential difference = same in each branch

Total resistance = decreases when adding resistance

IV graphs (required practical)

1. Turn on circuit

2. Take readings → plot points

3. Repeat for different current

Density equation

E = m/v

Mass / volume

How do you calculate density of a regular solid

1. Measure mass with balance

2. Measure sides with ruler

   → lxwxh = volume

How do you calculate density of a irregular solid

1. Measure mass with balance

2. Determain volume with eureka can and measuring cyclinder

How do you work or density of a liquid

1. Measure mass of an empty measuring cylinder

2. Fill cylinder of certain volume of liquid

3. Reweigh cylinder → difference = mass of liquid

What is pressure caused by

The forceof all the gas particles colliding with the walls of the container

Internal energy equation

Kintic energy + potential energy

Specific latent heat of fusion

Energy needed to melt 1kg, energy released when liquid freezes

Specific latent heat of vaporisation

Energy needed to boil/evaporate 1kg, energy released when the gas condenses

Specific heat capacity

Energy needed to heat 1kg of a substance by 1°c

Specific heat capacity (rp)

1. Measure m of block on balance

2. Measure temp at start with thermometer

3. Turn on power source for 10 minutes

4. Turn off power source to measure temp and energy from joulmeter

5. Calculate temp difference

6. Calculate specific heat capacity using E = mcø → C = E/mø

Calculate specific heat capacity (rp] improvements/safety

• add insulation/lid to reduce heat loss to surroundings (heat loss increases value found for C)

• plot E against ø → use gradient instead

Safety: block can get very hot (heatproof gloves or let cool)

Atom size

1×10-¹⁰m

Nucleus size

1/10,000 of an atom

Alpha particals :

Made up of, Distance travelled, stopped by, ionisation strength, example of equation

2 protons, 2 neutrons

Shirt (~5cm)

Paper

Strong

PO ²¹⁰84 → PO²⁰⁶82 + a⁴2

Beta particles:

Made up of, Distance travelled, stopped by, ionisation strength, example of equation

-e

Medium (~30cm)

Aluminium

Medium

CO⁶⁰27 → CO⁶⁰28 + Ɓ⁰-1

Gamma particles:

Made up of, Distance travelled, stopped by, ionisation strength, example of equation

Electro magnetic wave

Long (infinite in vacuum)

Thick lead or concrete

Weak

U²³⁵97 → U²³⁵97 + ƴ⁰0

Atoms absorbing and emitting EM radiation

Electron moves to higher energy level (absorb)

Electron drops to lower energy elvel (emits)

What is half life

1. Half the atoms/nuclei to decay

2. The count rate to drop to half

Uses of radioactivity

Sterling (kill bacteria on food)

Thickness control (count too high = too thin, count too low = too thick)

Carbon dating (using count rate and half life)

Radiotherapy (kill cancer cells)

Medical therapy (short half life, alpha can't leave body so beta or gamma)

Leak detection (detect where gamma sample count is highest = leak)

Smoke detector (alpha, smoke particals stop ionised particles reaching other side)

Irradiation

Hit by radiation

Protect with distances and materials that absorb

Contamination

Radioactive atoms on/in you (eg. Dust)

Keeps giving off radiation

Protect with suit/gloves/mouth cap (face mask)