Physics 10 Exam

8/8/2019 Physics 10 Exam

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Physics 10 Exam

Radioactivity

Bohr Model of the atom

Nucleus contains

- Protons- NeutronsOrbiting the nucleus are electrons

Isotopes are the same element with a different atomic mass (number of neutrons)

- Isotopes of a material are chemically identicalAtomic Number is the number of protons in a materialAtomic Mass is the protons plus the neutrons

Examples of Isotopes:

Hydrogen-1

1

H1

Hydrogen-2 (Deuterium)

2

H

1

Hydrogen-3 (Tritium, which is radioactive)

3

H

1

Recall that Water is H2O.

Heavy water is D2O.

- To get heavy water, you build large silos and fill them with water.- You let the water sit, so that the heavy particles fall down- Thus, you have heavier water at the bottom- You extract this heavy water, put it in a new silo, and the cycle goes on- D2O is used in nuclear reactors- Nazi Germany did this, but the Scandinavian Resistance stopped them

Radioactivity is the release of high energy particles and rays of energy from a substance asa result of changes in the nuclei of an atom

- It is the process of releasing rays outRadiation refers to the energy rays and particles emitted by radioactive sources

- Actual ray sent out- Light is a form of radiation humans can see

Atomic Mass

Atomic Number


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Why do isotopes exhibit radioactivity?

In a nucleus there are two forces

1 pulls together: this is the nuclear strong force

- Never complete dominant or else it would implode1 pushes apart: this is the nuclear weak force

- If the weak force is dominant, we get radioactivity- If both forces are in balance, we have a stable isotope with no radioactivityThe number of neutrons plays a critical role in the spacing of protons and neutrons in a

nucleus. Nucleus expands with more neutrons

Radioactive decay- Process by which unstable nuclei lose energy by emitting radiation- Unstable radioactive atoms undergo radioactive decay to form stable non-

radioactive atoms, usually made of a different element

Radioisotopes

- Natural or manmade isotopes that decay into stable isotopes, releasing radiationGreater space, more weak force, and then it blows apart (eventually)Nuclear Equation

237 233 4

U = Th + He

92 90 2

Charge and mass must be conserved

Types of RadiationAlpha Radiation

(Particle)

- A helium nucleus has +2 chargeo 4 atomic mass units (2p+, 2N)

- Alpha radiation occurs in an unstable nucleus where the weak force is dominant- The nucleus is falling apart- In an effort to become stable, it kicks parts of itself out (the helium)- The reactants atomic mass must be decreased by 4, and the atomic number must be

decreased by 2

237 233 4U = Th +

92 90 2

- Alpha particle= helium nucleus- This process tends to happen in larger elements

The helium nucleus

- A sheet of paper is enough to stop it

Reactant

Parent Isotope

Daughter Isotopes

Products


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- Because of its mass, it goes slower- Somewhat large +2 charge makes it sticky- This makes it bond to neutral/ positive matter

Beta Radiation

A Beta particle is a high speed electron with a -1 charge- Almost 0 amu- A sheet of tin foil can stop it- Its smaller size allows it to pass easier- In a sense, a Beta particle is better than an alpha particle because it has less charge

and almost 0 amu, making it lighter and faster

- Beta particle comes from the disintegration of a neutron1 1 0

N becomes p + e if it were to be disintegrated0 1 -1

Nothing happens to the atomic mass, but the atomic number goes up by 1

14 14 0

N becomes O +

7 8 -1

Gamma radiation

- Gamma Radiation is electromagnetic radiation (photons)o Pure energy

- No mass and no charge0

0

- It takes a 15 cm lead plate to stop it- Gamma Radiation is not directly caused by the nucleus.

60 60Co* becomes Co +

27 27

* denotes an excited electron state

Quantum Physics states that only certain orbitals are allowed for electrons.

Nucleus

You can have an orbit

here and here, but not

in between


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Electron energy loss is an electromagnetic wave

-The larger the orbit, the more energy required in the electronA is for Atom

-Atoms are very small-The atom is electrical

o Electrons are attracted by protonso Neutrons have no chargeo The atoms binding force, or cosmic glue, holds the nucleus together

-There are more than 90 basic elementso Identified by number of protons in nucleus

-Within each element can be different members-Isotopes

o Same number of protons but different number of neutronso Some elements have many isotopeso Some, like aluminum, have 1o Majority of atoms in an element are stable

-Some are radioactiveo They throw off rays along with protons and neutrons until they change their

own nuclear structure to become stable

o This changing of elements is natural transmutation-Scientists thought: can man change an atom?

o Artificial transmutation was achieved when a British scientist turnednitrogen to oxygen with an alpha particle

-What happens when you try to fire neutrons at uranium?o Nuclear fissiono The atom split into 2o The cosmic glue that holds together the nucleus has a mass of its owno The two atoms uranium split into had cosmic glue, but less than in the

original

o The extra binding force had exploded into energyo E=mc2

-When uranium is split, energy is releasedo Powerful rays similar to x rays are emittedo Free neutrons are driven off with speed

-If there is enough U 235 (critical mass= amount needed to set off chain reaction), thenneutrons are thrown out and hit other uranium atoms and split.

o Chain reactiono Yankee Stadium filled with dynamite = baseball of U235

-How do you get enough U 235 for a bomb?o Only a small amount of uranium is U 235

-At Oak Ridge, enough U 235 was separated to make a bomb-At Hanford, Washington, a huge plant was built


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o Furnace of atomic energyo You have graphite blocks in between rods of Uranium (U 235 and 238)o Graphite slows down free neutrons from U 235

Some hit other U 235 atoms Others hit U 238

o U 238 turns into neptunium which turns into plutoniumo Plutonium is fissionableo Source of atomic fuel

-This reactor produced heat, which can be used to provide electricityo Problems: Reactor needs to be shieldedo This adds lots of weight

-Research shows that many elements become radioactive when placed in a nuclearreactor

-Geiger Counter measures radiation-Isotopes are used a lot

o Agriculture: Isotopes test effectiveness of fertilizer and proper timing oftheir use

o Industry: Isotopes are used in the automatic control of sheet aluminum toensure accuracy

o Radioactive sodium helps doctors solve heart and circulatory diseaseso Radioactive phosphorus helps doctors to find tumors in the brain and to

simply operations for their removal

o Iodine 131 is used in the treatment of thyroid cancerRadiation

Units

1. Disintegrations per second = Becquerel (Bq)2. Energy carried by ray or particle= Gray (Gy)3. Effect on biological system= Sieverts (Sv)

Becquerels and Grays are used by chemists and physicists

Sieverts are used by doctors and biologists.

LD50

-Indicates that the lethal dose is 50-Kills half of them

LimitingDosage

-Limit timeo Less time, less dose

-Increase distanceo Farther distance, less dose

-Shieldingo Some material absorbs radiation

Electromagnetic radiation

From weakest to strongest

1. AC electricity


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2. Shortwave3. AM radio wave4. FM radio wave5. Microwave6. Infrared7. Red, Orange, Yellow, Green, Blue, Indigo, Violet8. UV rays9. X rays10.Gamma rays11.Cosmic Rays

C=f

C is the speed of light

F is the frequency is the wavelength

Question 1: Sodium Street lights emit a 532 nanometer light. What is the frequency of this

orange light?

3E8=f(532E-9)

3E8/532E-9= 5.6 x 1014 Hz

Recall that:

10-1= deci d

10-2= centi c

10-3= milli m

10-6= micro Q10-9= nano n

10-12= pico p101= deca D

102= hecto H

103= kilo K

106= mega M

109= giga G1012= terra T

Radioactive HalfLife

-Amount of time required for a parent nuclei to drop 50% in amount


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Asymptotic= approaches 0 but never reaches it

A= Ao(original amount) * 1/2t./half life

Radioactive Dating uses a chart to estimate age

A sample will have both daughter and parent isotopes

Adding both together gives you Ao

Transcendental Number= non repeating, non terminating decimal

In a solid material that gives off gas, estimating the gas from bubbles (porous) gives you the

original amount

Exponential Decay Curve


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Carbon 14 Dating

-Used to estimate age of biological things-How do we get it into biological things

o Inhalingo Eating

-Assumes that living things absorb radioactive material-Inhaling process relies on high atmosphere radiation

1. Some radiation is reflecteda. Some is transmutated into N14

2. Bob breathes in this N143. The N14 inside Bob turns into C144. When Bob dies, no more C14 is absorbed

Today, measurements show that there is a constant ratio between C14 and other Carbon

isotopes (namely C12) in the body

Mass spectrometer: Find out age by comparing C14 to other Carbon isotopes. If there is lessC14, you know that it has had time to decay.

We are assuming that the radiation we have today was the same as before

Only organisms that lived within the last 50,000 years have enough C14 for radiocarbon

dating

Nuclear Reactions

Fission= Large nucleus splits apart235 1

U + n

92 0

- A thermal neutron has a slower speed- It stops inside another U-235 atom- If it did not stop, it would go right through, accomplishing nothing

earth

radiation

Thermal

neutron


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- The neutron in the nucleus makes the weak force stronger, causing it to fissionThat can lead to (this is an example)

92 141

Kr + Ba

36 56

All the protons are accounted for, but the there are three neutrons missing (originally 236)So

92 141 1

Kr + Ba + 3 n

36 56 0- This leads to a chain reaction

The chain reaction stops when it runs out of material, or the neutrons leave

- The Critical mass (amount of material needed to sustain a chain reaction) needs toslow down the neutrons for a chain reaction to occur

Note: U 235 is not abundant

Little Boy bomb

The conventional explosive explodes, and the first piece of U 235 is shot at the other pieceCritical mass is achieved when both pieces of U 235 join.

Fat man bomb

- The explosives cause a perfectly symmetrical implosion.

Conventional U 235Explosive

Plutonium

Explosives


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- The plutonium is pushed together and makes critical massFusion reactions= multiple small nuclei join

3 1 4

H + H= He + E

1 1 2

This happens in stars everyday

Atomic Bomb

- Nuclear fissionThermonuclear Device AKA Hydrogen Bomb

- The atom bomb is the size of a briefcaseo It causes the conditions of the Sun for 1 microsecond

- The deuterium is basically a helium bombEarths core is molten because of uranium. The uranium forms a magnetic field

Nuclear Fission is in atom bombs and nuclear reactors (used for electricity)

Nuclear Fusion is used in hydrogen bombs

Fusion reactors are only experimental

- They give off as much energy as we put into it- Currently at break even

Plasma is a state of matter with no electrons

Mass Defect

235 1 92 141 1U + n Kr + Ba + 3 n + E

92 0 36 56 0

92 protons = 92 protons

144 neutrons = 144 neutrons

Kilogram mass > Kilogram mass here

- This is because the atomic glue has decreased- Mass must be conserved- Mass was converted to energy- So

Deuterium

Atom

Bomb


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E=mc2

M is the missing mass

C2 is the speed of light2

- Small amount of mass can be converted to a large amount of energyFission Reactors

- The control rod absorbs neutrons- It can be raised up and down- Canada uses heavy water in the moderator.- If you drain out the heavy water, the core goes inert (chemically inactive)

o This slows down neutrons- The US and Russia use mostly regular water and carbon- The Fuel Rods get hot- The heavy water coolant turns to steam- It is basically a big water boiler

The control rod is usually made from boronCanada uses heavy water in the moderator

The control rod is made of plutonium

Radiation and Biology

Iodizing Radiation can split a molecule into ions or radicalsNon iodizing radiation does not split the molecule, but can make the DNA go wonky

Iodizing Radiation and Non iodizing radiation can both cause somatic and genetic damage

Somatic Damage usually results in cancer, because the cell starts producing uncontrollably

Genetic damage causes mutants

F

UE

L

R

OD

F

UE

L

R

OD

MO

DE

RA

T

OR

CO

NT

RO

L

RO

D


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Non iodizing Radiation

Used in microwaves

The microwave causes the H20 to vibrate

Motion= heat

Electromagnetic radiation can affect ongoing chemical reactions

If it occurs in mitosis, for example, this can lead to duplication errors

The cell phone causes waves to go through your head

The wave gains resonance and this can cause brain cancer.

Standing wave: points at end are stationary, but the wave in between has a randomfrequency or intensity

AC electricity- High voltage power lines create an electromagnetic field- Dont live under them

Some other uses of non iodizing radiation

Smoke detectors

Use Americium 241

- Alpha particle source

DNA

Cell wall

If gamma radiation occurs here (does

not hit nucleus), the cell will try toneutralize the damage that happened

to the cell. In short, the nucleus hasthe ability to repair the cell

If gamma radiation passesthrough the nucleus, then

DNA damage can lead tosomatic damage or genetic

damage

H2O


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- Ionizing detector

If there is smoke rising, the Eparticles react with the smoke

The current is stopped, and an alarm goes off

Magnetic Resonance Imaging- Makes images of internal organs- Uses radio waves- Uses magnets

CAT scan- Uses X rays- Not good at seeing dense tissue- shows organ tear and injury well

Pion therapy

- uses powerful Pion beams for short periods to destroy tumorsRadioactive isotopes are used in hospitals for

Imaging, tracing, and removal

Heat

HeatEnergy

Heat is the amount of kinetic energy measured in joules contained within an object

- movement of particlesTemperature is the average energy per particle

- measured in degreesHeat transfers from one object to the next when there is a difference in temperature

It is possible to have the same temperature but with different heat energy

- if you have 45 tons at room temperature, there are more particles and more energyas compared to 1 ton at room temperature

Specific heat is the amount of energy needed to change 1 kg of matter by 1 Celsius

Am-241E E

Electric

Target

More

energy

Less

energy


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4180 4200 J (specific water of H2O)

- this is the amount of needed to change 1 kg of H2O by 1 Celsius(H=mc(T

(H is the change in heat energy

M is massC is specific heat capacity

(T is the change in temperature

How much electrical energy is required to heat 450 ml of H2O from room temperature

(22 Celsius) to boiling point (100 Celsius)

(H= ?M= .45 kg

C= 4200

(T=78 Celsius

(H=147420 J

Measuring heat energy is called calorimetry

Measuring HeatEnergy

Celsius reference points

- uses freezing point of pure H2O (0 Celsius)- uses boiling point of pure H20 (100 Celsius)- This is at sea level (standard pressure)- -273 Celsius is absolute zero

Fahrenheit uses body heat as a reference

- Tried to use 98F for body heat as reference point- Poor choice because body heat fluctuates- So then they used the freezing point of brine as a reference point (0F)- Freezing point of pure H20 is 32F- Boiling point is 212F

Kelvin

- Uses absolute 0 as a reference point- 0 degrees Kelvin is absolute 0- Absolute 0 means there is 0 temperature, and 0 movement- This is impossible; even if you are in a vacuum there is still energy such as radiation

Celsius and Fahrenheit cross at -40

Converting

Kelvin= Celsius + 273

Celsius= 5/9(f-32)

More energy Less energy


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Fahrenheit= 9/5C+32

Heat transfer

Conduction

- Heat travelling in a solid- Travels via bonds- Bonds act like springs- Mechanical energy sent via bonds in atoms of a solid- Insulators prevent heat travelling- Conductors allow heat to travel (e.g.: metals like copper or aluminum)

Convection

- Happens in fluids (gas/liquid) through collisions- Molecules will travel until they hit other molecules, giving away some energy

Radiation- Electromagnetic waves- Does not require matter- E.g.: microwaves cause motion in molecule, and makes heat

Recall that heat moves when there is a difference in temperature

Hot to cold

Convection cells

A heat source causes molecule speed to become faster. The spacing between moleculesincreases, and there is less density

The low density rises- The fluid then cools, so the speed slows down and the density increases- The Fluid falls- The cycle restarts


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Heat transfer in local environments

TH2O T land (at middle of night)

H2O

C=4180 J/kg c C= less than 1000 J/kg c

C is specific heat capacity

- At midnight there is no heat transfer because the temperature of the water and ofthe land are approximately equal

H2O Land

- Heats up slower - heats up faster

- The wind blows towards the shore- The air over the hot land tends to rise

vacuum


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Just after sunset

Water Land

Higher Joules Less JoulesHigher temperature Less temperature

- Wind blows away from landGlobal Convection- Pt 1 Atmosphere

- Doldrums are areas north of the equator with no wind/ light winds situatedbetween trade winds

- Trade winds are prevailing tropical winds that blow towards the equator- Solar radiation results in heating at the equator- This directly results in the Hadley cell- The polar cell occurs at 60 North

o Cold air descends over the North pole, causing pressureo Cold air moves down to lower latitudes (60) and starts a convection cell

- Ferrell cell is a result of movement ofPolar and Hadley cellsEarth GeologySources ofEarth Heat

1. Latent heat of Earths formation (Gravitational compression is related)2. Sun (Solar Radiation)3. Radioactive decay (Uranium/Radium decaying into more stable elements)

Vacuum

Trades= lots of wind

Doldrums= no wind

Equator

Trades= lots of wind

H

PF


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Global Convection Part 2 Geology

The convection cells form Subduction zones, trenches, and ridges

Spin

- Atmospheric effect- Coriolis effectis a change in the direction of moving air, water, or objects due to

Earths rotation

o Coriolis effect and convection currents results in trade winds, prevailingwesterlies and polar easterlies

o Move east to negate Coriolis effect- Friction between surface and air

o Air moving on the surface starts moving in the same direction as the spino The earth rotates east, and the wind blows east

- A jet stream forms in the upper troposphere due to convection currentso Become bands of fast moving air in the stratosphereo Very strong, so airplane pilots try to fly with themo Enhanced by cooler temperatureso Fastest at the equator, because there is more spin there

1. First, the Sun gives Earth heat2. This is reflected partially3. But the CO2 reflects this back making our earth warmer

Outer core

core

Mantle

CrustSubduction zone/trench

ridge

CO2


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4. The ice caps are melting (area covered shrinks)5. Shrinking ice caps means more heat is absorbed

Albedo is the ability to reflect heat

Low albedo= black asphalt parking lot

High albedo= glacier (white)

El Nino

- Extremely weak westerly trade winds allow warm Pacific waters to move eastward- Stops cold water from upwelling- Warmer weather

La Nina

- Strong westerly trade winds allow cooler water to upwell- Brings colder temperatures to Northwestern North America

Layers of the Atmosphere1. Troposphere

a. Where weather occurs2. Stratospherea. Where most ozone isb. Protects us from ultraviolet radiation

3. Mesospherea. Protects us from meteors

4. Thermospherea. Where aurora occurs

5. Exosphere connects to spaceLatent Heat

- If you have 100 of water and 100 of steam, the only difference is that the gas hasmore energy

Gas

Latent heat

LiquidTemp. 0 latent heat

-C

- Latent heat is the energy needed to change a phase of matter- At 0if you add energy, the ice will not change in temperature until it becomes a

liquid


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- At the second latent heat period, the food (if cooking) absorbs all the energy beforeliquid turns to gas

- If steam touches colder food, it condenses- The food absorbs this steam turned water- The water is turned back to steam, so it is a cycle

Liquid in plants can turn to gas without heating up. This is called Transvaporation. Thus if

you have more plant life, it is colder

Vectors and Scalars

- Vector is a physical quantity with both Magnitude and direction- Magnitude means size- An example of a vector is force- If Bob punches me. This is a vector because there is size (big or small hit) and

direction (where does he hit)- Scalars include magnitude only

o Masso Temperature

Distance (scalar)

- Length between two points- Measured in meters- Scalar

Displacement (vector)

- Distance with direction- Vector- Measured in meters or km

Displacement vs. Distance

- If I walk from A to B (10 meters apart), and return, the total distance is 20 meters- The Total displacement is not because one direction is positive and one is negative

(+10 m and -10m). Total displacement is 0

Velocity (vector)

- How quick an object is moving- I come to school from home for 4 km. You come to school from fome for 13 km. Who

was faster?

o Indeterminateo You need both distance and time

- Velocity= distance/time- Distance travelled per unit time

Average velocity is total displacement/total time

- A car leaves home on km 21 of the Alaska highway at 12:00 pm- At 12:45 pm, the car is at km 18 of the Alaska highway


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- What is the cars displacement, what was the time interval, what is the cars averagevelocity?

To find total displacement, you do (df-di)

Displacement: 18-21= -3km= -3000 m

Time interval: 45 minutes= 2700 s

Vav= -3000/2700= -1.1 repeating m/s

Think of a number line

Positive is to the right (or up)

Negative is to the left (or down)

Speed (scalar)

- Velocity without direction- Average speed is total distance/ total time

Position

- Distance relative to a point of referenceAcceleration (vector)

- Rate of change in velocity- Vector- For example, in a drag race, the speed changes- If you have something going around in a circle at uniform speed, acceleration still

changes because of direction

- Slowing down is negative accelerationAav= total velocity/ total time

Indiana Jones mine railcar goes from 5 m/s to .2 m/s as it goes up a hill in 4 seconds. Whatis the average acceleration?

-4.8 m/s 4s

-1/2 m/s2

How long does it take for the rail car to come to a complete stop from its initial speed?-1.2 m/s2= 0-5 total time

-5-1.2

4.1666(etc.) s

Distance time graph of uniform motion


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Positive velocity

- Constant velocityThe displacement is changing

Velocity Time graph Equivalent

X axis

- Constant positive velocityAcceleration time graph equivalent

At x axis because there is no acceleration (constant velocity)

Distance time graph for negative constant velocity

Negative velocity

- Constant


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Velocity time equivalent

X axis

Acceleration time graph equivalent

Line is at x axis again

Distance time graph for stopped object

X axis

In this case, the object is at rest past the reference point

Velocity time graph equivalent


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At x axis

Acceleration time graph equivalent

at x axis

Distance time graph for increasing acceleration

d-t

The line is a concave up

Velocity time graph equivalent

Increasing velocity

Acceleration time graph equivalent for concave up


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X axis

Constant acceleration

Distance Time graph for concave down

Velocity time graph

Slope is negative

Negative accelerationWhen it reaches 0, the speed is 0, then it starts going backwards

A-t equivalent is

X axis


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Practice:

First, the guy speeds up, then there is 0 movement, then there is negative acceleration

Gravity

At the earths surface all objects accelerate at g=9.81 m/s2 excluding other forces (airresistance and friction)

-A lighter object and heavy object land at the same time if dropped at the same timeA gravimeter (measures gravitational field) can find pitchblende and deposits of oil.

Uranium is mined from pitchblende. If you fly with a gravimeter over it, then the number

decreases

If you fly over something like oil, then the number goes down.

Practice

A plane falls off a ledge without its propellers on. Then James Bond jumps after it a few

seconds after watching it and sitting on the ledge.

distance time graph

The acceleration is essentially the same between the two. But the plane has had time to

accelerate, and this the gap between the airplane and Bond increase simply because Bondjumped later. The acceleration is the same though.

Velocity time graph

Acceleration time graph


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X axis

-9.8 m/s2

Practice 2

I drop a penny from a cliff into a dark pit. I wait 8.5 seconds and then I hear it land. How

deep is it?

D=vi t + 1/2at2

Coin has no speed at the beginning.

So vi=0D=1/2at2

A=-9.81So d=(1/2)(-9.81)(8.52)

D= -354.4 m

Practice: Graphing a Displacement time graph

Fictional scenario

You can make a velocity time graph from this by using the slope of the displacement time

curve

As the slope of a velocity time graph increases, the velocity increases

- If the displacement time graph curves up, then there is accelerationThe slope of a displacement time graph is basically the velocity.

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Physics 10 Exam