Physics Test #2

a piece of roof that is 400 km tall and 600 km wide How much rooftop area is required to power a household with solar? How much land is required to produce power output of a large powerplant w solar?

area: 240,000 km squared power output: (240,000)(10 to the 6th w/km squared) input: 5 times 10 to the third watts= 240 gw

Field produced by a + charge at a nearby location points:

away from the charge (field always points away from the charge)

energy storage problem

batteries are expensive

which nucleus stores more nuclear potential energy c-14 or n-14

c-14 (starts as high npe and low ke, then has low npe and high ke)

1/16th of carbon is taken from the body

carbon has half life of 5700 and 1/16th is 3 half lives (2 to the 4th) so 5700 yimes 4 equals 23,000 years old

body is found, carbon is removed and found to be 1/8th as radioactive as fresh carbon how old is the body?

carbon is half life 5700, 1/8th is 3 half lives (2 to the 3rd) so 5700 times 3 equals 17,000 years old

(# now)/(# initial) = 2^(# of dt's elapsed)

chain reaction dt is doubling times passed

a CURRENT CARRYING wire creates a MAGNETIC FIELD

current carrying wire: electrons move through it magnetic field: field "circulates" around the wire; it exerts a magnetic force on any charge that moves at an angle relative to the field

what is not a possible fission product? a. sr-90 b. cs-137 c. i-131 d. th-234

d. th-234 because fission products will have to be small bc they can break into smaller pieces

what happens to strength of a permanent magnet as its temp is increased

decreases

the "doubling time" for a fission reaction inside solid uranium-235 is roughly .010 microseconds, once the first nucleus undergoes fission, how long does it take for 10 to the 24th or 2 to the 80th u-235 nuclei to undergo fission

dt= .01 microseconds 2 to the 80th is 80 doubling times so take 80 times .01 and it equals 1 microsecond

1/2 life

each unstable nucleus has this, exactly half of the nucleus will explode in one half life

draw an electric motor and explain

explanation: a lasso, electrons enter and go around the wire with a opposing magents on either side that make the machine move or jiggle this 'electromagnet' reverses the flow of electrons (can be turned on or off and it can vary in strength; is highly efficient) also elecpe -> ke the field pushes electrons up or down the "electric motor"

(# remaining)/(# initial) = 1/(2^(# of hl's elapsed))

exponential decay in radioactivity and half lives

electric motor examples

fan, audio speaker, hair dryer, blender, an electric kettle, a vaccum

BETA MINUS DECAY if the inital is c-14 (6 protons and 8 neutrons)

final is n-14 (7 protons and 7 neutrons) electrons fly off as radiation rays and antineurons

induced fission of u-235 initial is

final is that it produces 2-3 neutrons fragments (the specific energy is 10 to the 6th times any chemical fuel

ALPHA DECAY (bigger nuclei) if the inital is u-238 (92 protons and 146 neutrons)

final is thorium-234 (90 protons and 144 neutrons) losing a helium 4 as radiation rays

supercritical

growing chain reaction will explode

How often is it sunny and how does that affect photovoltaic cells?

it's sunny about 33% of the time and solar photovoltaic cells are only ~20% efficient

how does electricty spin a blender?

like using motion to get electric potential energy (electric generators) like a turbine in a steam engine or the hydroelectric turbines in the hoover dam (need a wire carrying current through the magnetic field which causes the wire to move up and down leading to the blender moving electrons) use a battery to make electrons move along the wire

what is lnt

linear no threshold model: states that no matter how much radiation it will always pose as some risk

what is the hurdle to making a uranium bomb?

most nuclei are u-238 (not 235) and it cannot be separated by chemistry only enrichment so it is hard to obtain takes a long time

how is fission similar to radioactivity?

much greater specific energy than chemical reactions

Suppose that the ¤ symbol shown below represents the cross section of a wire that runs perpendicular to the plane of this page. Suppose that electrons flow out of the page along this wire. If a compass were placed at point P, which direction would the north pole of the compass point? (Refer to picture #2.) electrons -> ¤ P

n pole of compass would point kind of up and at a vertical angle (ne)

subcritical

no explosion

magnetic field exits through..

north

south pole is?

north magnetic pole

problem w solar and wind power?

only provide power intermittently

An electric field arrow at a given location push a - charge in what direction?

opposite direction as the arrow

Which poles attract?

opposite poles (N&S)

where do australias magnetic field lines go

out of the ground

magnetic force

perpendicular to the field and perpendicular to the direction of motion

magnetic force is

perpendicular to the magnetic field and perpendicular to the direction of motion

which nucleus stores more npe pb-206 or po-210

po-210 (po turns into pb by losing 4 atoms helium 4)

an atomic nucleus:

protons and neutrons should repel in the nucleus but are held together by some 'strong nuclear force' which is often caused by the fact that there are usually more neutrons

what kind of nucleus results after u-239 undergoes 2 consecutive beta minus decays

pu-239 because 2 neutrons change into protons

nuclear induced fission how is it different from radioactive decay?

roughly equal sized pieces and is initiated by a neutron

One centimeter =

roughly the width of a pinky finger tip

radioactivity

some atomic nuclei spontaneously explode (unstable) and some don't (stable nuclei) EX: alpha decay; beta plus decay, and beta minus decay

magnetic field enters through...

south

north pole is?

south magnetic pole

An electron is released from rest at a location where the electric field points to the right. Which direction will the electron begin to move?

to the left

Field produced by a - charge at a nearby location points:

towards the charge

BETA PLUS DECAY inital is c-11

turns into b-11

BETA MINUS DECAY initial is lead214

turns into bi 214

c-14 undergoes beta minus decay w hl of 5700yrs

turns into n-14

co-60 undergoes beta minus decay with a half life of 5 years

turns into ni-60

ALPHA DECAY initial is radium222

turns into rn 218

what kind of nucleus results immediately after u-238 nucleus absorbs a neutron

u-239

what is an electric generator

uses ke to make elec pe, starts as ke a moving turbine and then it creates it into elec pe by using the magnetic force to move the electrons by putting a n ---> s grab the wire and pull it up and down which causes the electrons to go up and down and electricity (wire) is going in and out of the board

if 10 kg of u-235 undergoes fission the energy released is equal to ____ of dynamite

using the specific table (80,000 times 10 kg)/5 = 160million kg

Due to the direction and charge of an electron/proton when does it speed up or slow down?

+ and + repel -> slow down + and - attract -> speed up - and - repel -> slow down

How much energy is required to put a fallen apple back on the apple stand

1 Joule

How much electric power is consumed by typical US household?

1000 watts 1 kw

1 Mega Joule =

10^6 Joules

airplane pilot accumulates 200 millisieverts, whats the increase in cancer risk?

200(.005)= 1% increase

cobalt-60 in 2013, it beta decays to ni-60 w a half life of 5 years, in what amount of years is it found to be 75% ni-60?

2023 (1/2 to the 2nd) is 1/4 and is 2 half lives 10 + 2013

1 meter =

3 feet

doubling time equation

70%/growth rate

What plutonium isotope fissions?

Pu-239

An electric field arrow at a given location push a + charge in what direction?

Same direction as the arrow

x ray technician gives 10,000 x rays per years for 20 years, each x ray gives .02 millisievert, estimate number of cancers caused by this radiation

(.02)(.005)= .0001 take that times 200,000 (10,000 times 20) which is a 20% increase because 1 in 5 techs probs caused cancer so this person caused between 0 and 1

dental x rays deliver full body dose of .1 millisievert so what is the persons risk of developing cancer?

(.1)(.005) equals .0005 + to 40% chance of cancer so you have a 40.0005% risk

Equation for likelihood of cancer

(0.005%)(Radiation dose in millisievert)

How much solar power is landing on earth's surface?

1 gw per kilometer squared (during sunny times) or 1 kw per meter squared

1 Watt =

1 joule per second

what is 2 in binary?

1 times 2 to the 1 + 0 times 2 to the 0 (10)

what is 167 in binary?

1 times 2 to the 7th + 0 times 2 to the 6th + 1 times 2 to the 5th + 0 times 2 to the 4th + 0 times 2 to the 3rd + 1 imes 2 to the second + 1 times 2 to the 1 + 1 times 2 to the 0 = 10100111

How much electric power is produced by windfarm?

1,000,000 W (or 1 MW) per square kilometer

How much electric power is produced by a large power station?

1,000,000,000 W (or 1 GW) or 10 to the 9th watts

binary

2 to the 0 all the way to 2 to the 8th,

What is the percentage of americans to get cancer?

40%

What is an electric field?

An electric field is a region of space around an electrically charged particle or object in which an electric charge would feel force

Which poles repel?

Like poles (N&N, S&S)

A lady standing in San Diego uses a compass to determine the direction of Earth's magnetic field at her location. She then points a charged-particle gun in that direction and fires. Does Earth's magnetic field exert a force on these particles? If so, does that force point along a longitude line or along a latitude line?

No, its moving along the field

npt

Nuclear Non-Proliferation Treaty: no more development of weapons or nuclear. if you have them you can't use them or keep developing. while countries without cant start

An electron is moving east when it enters a region where the electric field points to the east. Will the electron speed up or slow down in this region?

Slow down, field pushes opposite direction of motion

A proton is moving east when it enters a region where the electric field points to the east. Will the proton speed up or slow down in this region?

Speed up, field pushes along direction of motion

What was the first uranium bomb created?

The "little boy"

What uranium isotope fissions?

Uranium-235 (92 protons and 143 neutrons)

Which uranium isotope is more common than Uranium -235 but doesn't fission?

Uranium-238 (92 protons and 146 neutrons)

A guy standing in Quito, Ecuador points a charged-particle gun straight upward (not northward) and fires. Does Earth's magnetic field exert a magnetic force on these particles? If so, does that force point along the equator or along a longitude line?

Yes, it goes along the equator

electric field

a condition of where each location associated with it

What is enrichment?

a measure of how much stuff is in U-235

What is a growing chain reaction?

a process where in one thing produces two or more equivalent things, and each of those things produce two or more and so on, (like exponential growth in the penny method) also when 1 n turns to 2-3 n a chain reaction is possible

what shape has a small critical mass?

a sphere, the bigger your critical mass means you needed a lot of items to fission, and the smaller your critical mass you did not need very much

electric charge

affects the electric field and exerts a force on the electric charge

difficulties creating the fat man bomb

that the implosion requires to have the technology that sets off all of the TNT at the same time simultaneously

using motion to get electric potential energy

the field pushes electrons along the wire (current) in and out of the page to make an electric generator

ltbt and

this treaty everyone who signed agreed to not test or only test in certain ways