Posts by J

Total # Posts: 1,028

physics
A sample of charcoal from an archaeological site contains 55 g of carbon and decays at a rate of .877 Bq. How old is it? ok I am totally lost, I don't know where to start

Physics
A sample of charcoal from an archaeological site contains 55 g of carbon and decays at a rate of .877 Bq. How old is it? ok I am totally lost, I don't know where to start

Physics
I don't know how to get the frequency, I think if I can figure that out I could get the rest, but I am not sure where the two 75 W come in and the 5% like where am I suppose to put them in any equation?

Physics
A 75 W light source consumes 75 W of electric power. Typically only about 5% of this energy is emitted as visible light of wavelength 600 nm. (a) Calculate the frequency of the emitted visible light. (b) How many photons per second of visible light does the source emit? (c) Is...

Physics
A laser used to weld detached retinas emits light with a wavelength of 652 nm in pulses that are 20 ms in duration. THe average power expended during each pulse is .600 W. (a) How much energy is in each pulse, in joules and electron volts? (b) What is the energy of one photon ...

Physics
What is the thinnest film of a coating with n=1.42 on glass n=1.52 for which destructive interference of the red component (650 nm) of an incident white light beam in air can take place by reflection? I am confused on the n's and I have no idea what equation to use, it ...

Physics
Coherent light of frequency 6.32 * 10^14 Hz passes through two thin slits and falls on a screen 85 cm away. You observe that the third bright fringe occurs at +- (plus or minus) 3.11 cm on either side of the central bright fringe. (a) How far apart are the two slits? (b) At ...

Physics
Two small stereo speakers A and B that are 1.4 m apart are sending out sound of wavelength 34 cm in all directions and all in phase. A person at point P starts out equidistant from both speakers and walks so that he is always 1.5 m from speaker B. For what values x will the ...

us history
What gropu was largely responsible for funding the builing of the railroad system in the U.S.?

Physics
A certain digital camera having a lens with focal length 7.5 cm focuses on an object 1.85 m tall that is 4.25 m from the lens. (a) How far must the lens be from the photocells? (b) How tall is the image on the photocells? Is it erect or inverted? (c) A SLR digital camera often...

Physics
You want to take a full length photo of your friend who is 2 m tall, using a 35 mm camera having a 50 mm lens. The image dimensions of 35 mm film is 24 mm by 36 mm, and you want to make this a vertical photo in which your friend's image completely fills the image area. (a...

Physics
You want to take a full length photo of your friend who is 2 m tall, using a 35 mm camera having a 50 mm lens. The image dimensions of 35 mm film is 24 mm by 36 mm, and you want to make this a vertical photo in which your friend's image completely fills the image area. (a...

Physics
A certain digital camera having a lens with focal length 7.5 cm focuses on an object 1.85 m tall that is 4.25 m from the lens. (a) How far must the lens be from the photocells? (b) How tall is the image on the photocells? Is it erect or inverted? (c) A SLR digital camera often...

science
Why is the mechanical advantage of an inclined plane less than 1

Physics
The crystalline lens of the human eye is a double convex lens made of material haveing an index of refraction of 1.44. Its focal length in air is about 8 mm which also varies. We shall assume that the radii of curvature of its two surfaces have the same magnitude. (a) Find the...

Physics
A mirror on the passenger side of your car is convex and has a radius of curvature with magnitude 18 cm. (a)Another car is seen in this side mirror and is 13 m behind the mirror, if the car is 1.5 m tall, what is the height of its image? I can't figure this one out! help ...

Physics
my book says the answer is 39 degrees..

Physics
If the critical angle for light at an interface between certain substances is 54.2 degrees, what is the polarizing angle at this same interface? I am confused!

math riddle ALGEBRA WITH PIZZAZZ
How does a hawaiian baritone laugh? A -low- ha

Physics
During 2004, japanese scientists successfully tested two solar sails. One had somewhat complicated shape that we shall model as a disk 9 m in diameter and 7.5 um thick. The intensity of solar energy at this location was about 1400 W/m ^2. (a) What force did the sun's light...

Physics
We can reasonaly model a 75 W incandescent lightbulb as a sphere 6 cm in diameter. Typically, only about 5% of the energy goes to visible light; the rest goes largely to nonvisible infrared radiation. (a) What is the visible light intensity (in W/m^2) at the surface of the ...

Physics
Medical x rays are taken with electromagnetic waves having a wavelength around .1 nm. What are the frequency, period, and wave number of such waves? ok I got the frequency as 3 * 10^18 Hz and the wave number as 6.3 *10^10 rad/m but I can't seem to remember how to get period.

Physics
In TV picture, faint, slightly offset ghost images are formed when the signal from the transmitter travels to the receiver both directly and indirectly after reflection from a building or some other large metallic mass. In a 25 inch set, the ghost is about 1 cm to the right of...

Physics
ok thank you! I wasn't using the right numbers!

Physics
When a solar flare erupts on the surface of the sun, how many minutes after it occurs does its light show up in an astronomer's telescope on earth? I am totally confused..help!

Physics- energy
Question 1The best way to determine levelness is to see if slope of velocity versus time for both directions are equal but opposite. Question 4:The greatest magnitude of net force is when the cart is going uphill. Uphill has a Net force greater by twice friction. It is not ...

cultural diversity
What is a current issue between Native Americans and the Federal Government. Indentify the legislation that you think is linked to the issue, and explain why you think there is a connection. Help Please!

Physics
An inductor used in a dc power supply has an inductance of 12 H and a resistance of 180 ohms and carries a current of .300 A. (a) How much energy is stored in the magnetic field? (b) At what rate is thermal energy developed in the inductor? ok once again I got part (a) .540 J...

Physics
A transformer consists of 275 primary windings and 834 secondary windings. If the potential difference across the primary coil is 25 V, (a) What is the voltage across the secondary coil? (b) what is the effective load resistance of the secondary coil if it is connected across ...

Physics
An inductor used in a dc power supply has an inductance of 12 H and a resistance of 180 ohms and carries a current of .300 A. (a) How much energy is stored in the magnetic field? (b) At what rate is thermal energy developed in the inductor? ok once again I got part (a) .540 J...

Physics
A transformer consists of 275 primary windings and 834 secondary windings. If the potential difference across the primary coil is 25 V, (a) What is the voltage across the secondary coil? (b) what is the effective load resistance of the secondary coil if it is connected across ...

Chemistry
What is the mass in grams of 1.02X10^24 molecules of NaCl?

Physics
A closely wound rectangular coil of 80 turns has dimensions of 25 cm by 40 cm. The plane of the coil is rotated from a position where it makes an angle of 37 degrees with a magnetic field of 1.10 T to a position perpendicular to the field. The rotation takes .06 s. What is the...

Physics
A coil of wire with 200 circular turns of radius of 3 cm is in a uniform magnetic field along the axis of the coil. the coil has R=40 ohms. At what rate, in Teslas per second, must the magnetic field be changing to induce a current of .150 A in the coil? I don't know if I ...

Physics
ok I am confused, because I have the answer in the back of my book it says it is D/square root of 2

Physics
If a magnetic flux passes through a circular coil when its diameter D, what should be its diameter (in terms of D) so that only half as much flux passes through it in the same field? Assume that the magnetic field is uniform over the area in both cases. I am totally lost! I ...

english
Okay. Thank you for your help.

english
Do I have to make them specific if that is my top sentence for a paragraph that relates back to this thesis: The characters of the novel demonstrate how misery drives people to do things they would not normally do.

english
how can i word this differently: People advise others to stay clear of the horrible consequences of despair.

English
Thank u so much. that helped a tons. So the other ones don't need any commas? (that's what i'm worried about). thanks again.

English
Can someone please check the grammar in the following sentences. Please. 1. Normally Victor takes pleasure in spending time with his family; however, when he feels down he opts for solitude. 2. The creature begins to feel alone and vows revenge. 3. This is the same creature ...

Physics
An electron beam of a TV picture tube is accelerated through a potential difference of 2.00 kV. It then passes into a magnetic field perpendicular to its path, where it moves in a circular diameter of .360 m. What is the magnitude of the field? I am lost. I keep getting the ...

english
Thanks

english
when citing long quotes do i put the parentheses with the page # after the period or before? thanks for ur help.

English
thanks

English
Is this a strong thesis: The characters of the novel demonstrate how misery drives people to do things they would not normally do.

English
does this need a comma: Over six billion souls in the world and they all have something in common. Thanks for ur help.

Physics
A beam of protons is accelerated through a potential difference of 0.745 kV and then enters a uniform magnetic field traveling perpendicular to the field. (a) What magnitude of field is needed to bend these protons in a circular arc of diameter 1.75 m? (b) What magnetic field ...

science
25. A 34g Cu * 1 mole Cu/ 63.54 which equals .54 26. A

History
HOW AND WHY DID WARFARE CHANGE IN THE 20TH CENTURY?

Physics
In designing a velocity selector that uses uniform perpendicular electric and magnetic fields, you want to select positive ions of charge +5e that are traveling perpendicular to the fields at 8.75 km/s. The magnetic field availabe to you has a magnitude of 0.550 T. (a) What ...

Math
What is the area of a circle that is 6m in square centimeters

english
What does nature is not benign mean?

Physics
The internal resistance of a dry cell increases gradually with age, even though the cell is not used. The emf, however, remains fairly constant at 1.5 V. Dry cells must be tested for age at the time of purchase by connecting an ammeter directly across the terminals of the cell...

Physics
ok yea! I got it now..I just made a stupid mistake with my algebra! Thank you!

Physics
ok I used 1.512 = 1.484[1+ alpha (34-20)] and the answer in the back of my book isn't the answer I am getting

Physics
A certain resistor has a resistance of 1.484 omega at 20 degrees celsius and a resistance of 1.512 omega at 34.0 degrees celsius. What is its temperature coefficient of resistivity? ok..I used a temperature equation but I can't get the right answer. so maybe I am doing ...

Physics
(a) How much charge does a battery have to supply to a 5.0 uF capacitor to create a potential difference of 1.5 V across its plates? How much energy is stored in the capacitor in this case? (b) How much charge would the batter have to supply to store 1.0 J of energy in the ...

Physics
A 450 uF capacitor is charged to 295 V. Then a wire is connected between the plates. How many joules of thermal energy are produced as the capacitor discharges if all of the energy that was stored goes into heating the wire? I am totally confused I don't even know where to...

Chemistry
The density of gold is 19.3 g/cc (g/ml). If a gold rod has a diameter of 4.20cm and 8.0 cm long. What is the mass? I just need to know if I did this right... r= 2.1 3.14 x 2.1^2 x 8.0 = 110.835g 19.3 g/cc x 110.835g = 2139.12 g/ml m = 2139.12

Physics
(a) If you use two quarters 2.00 mm apart to make a parallel plate capacitor, what is its capacitance? Measure the necessary quantities. (b) If you connect your capacitor in part (a) across 12 V potential difference, how much excess charge will flow onto each quarter? I am ...

Physics
A paralle plate air capacitor has a capacitance of 500.0 pF and a charge of magnitude 0.200 uC on each plate. The plates are 0.6 mm apart. (a) What is the potenetial difference between the plates? (b) What is the area of each plate? (c) What is the electric field magnitude ...

physics
A parallel plate capacitor having plates 6.0 cm apart is connected across the terminals of a 12.0 V battery. (a) Being as quantitative as you can, describe the location and shape of the equipotential surface that is at a potential of +6.0 V relative to the potential of the ...

physics
A point charge Q= 4.60 uC is held fixed at the origin. A second point charge q=1.20 uC with mass of 2.80 * 10^-4 is placed on the x-axis 0.250 m away from the origin. (b) The second point charge is released from rest. What is its speed withn its distance from the origin is (i...

physics
A neutral conductor completely encloses a hole inside of it. You observe the outer surface of this conductor carries a charge of -12 uC. (a) Can you conclude that there is a charge inside the hole? If so, what is the charge? (b) How much charge is on the inner surface of the ...

physics
During a violent electric storm, a car is struck by a falling high-voltage wire that puts an excess charge of 850 uC on the metal car. (a) how much of this charge is on the inner surface of the car? (b) How much is on the outer surface? ok...I didn't think there was any ...

physics
ok..thank you very much. I thought that is what you would do for part b but I wasn't sure! Thank you!

physics
(a) How many excess electrons must be distributed uniformly within the volume of an isolated plastic sphere 30.0 cm in diameter to produce an electric field of 1150 N/C just outside the surface of the sphere? (b) what is the electric field at a point 10.0 cm outside the ...

physics
ok so the length of the sides doesn't matter in this case? I am confused! haha

physics
ok the question is....A point charge of 8.00 nC is at the center of a cube with sides that are 0.200 m. What is the electric flux through (a) the surface of the cube, (b) one of the six faces of the cube? ok so would I just use Gauss's law 4* pi*k*q? even though that is ...

physical science
jxdjruhj3468

physics
(a) What is the total negative charge, in coulombs, of all the electrons in a small 1.00 g sphere of carbon? One mole of C is 12.0 g, and each atom contains 6 protons and 6 electrons. (b) Suppose you could take out all the electrons and hold them in one hand, while the other ...

English
please can somebody tell me the effects of a metaphor, onomatopoeia and extended personification are. thank you please reply

social
what is the name of the publication of the American automobile assocation?

Math - Statistics
Oh i'm sorry: The check-out can process a total of four customers every minute.

Math - Statistics
Suppose that the mean number of customers who arrive at the check-out counters each minute is 4. Create a Poisson Distribution with u (lamda) = 4 for x = 0 to 20. Compare your results to the histogram. 20 random numbers are generated with a Poisson distribution for u (lamda...

chemitsry
The directions say for each of the following use appropriate chem properties to explain the following observations. What would be observed on the surface of zinc and silver if they are placed in separate solutions of copper (II) sulfate? I am not really sure what they're ...

Biology - photosynthesis
1. In measuring the amount of ATP and NADPH consumed by the Calvin cycle, you find 30,000 molecules of ATP consumed but only 20,000 molecules of NADPH. WHere did the extra ATP molecules come from? A) Chlorophyll B) photosystem II C) cyclic electron flow D) noncyclic electron ...

Science
USA. Waste. Thats the topic the title of my work to give you what i'm talk about.

Science
SUM1 PLEZ HELP ME

Science
Topic: Waste Minimization How bad is it locally (USA)?

spaish
Hello, Hi

Science
Who is creating the most waste?What is suggested that we do to curve the waste problems? What is already being done to help curve the waste problem?

science
what are the future effects/impacts of landfills?

science
Who is creating the most waste?What is suggested that we do to curve the waste problems? What is already being done to help curve the waste problem?

Science
What are waste minimization components?

Science
How is waste minimization bad locally in USA?

social studies
What is a dissenter?

GRAMMAR
A comma?

GRAMMAR
Do I use a semicolon correctly in this sentence? "This caused David to become a spectator rather than a sufferer; covering his misery with mercy and sadness with compassion (3.2.4)."

REPOST biochem
i don't understand this why can carboxyl and phosphate groups act as acids? as in, what makes an acid?

Biology
nevermind i figured it out

Biology
What's high specific heat is mainly a consequence of the: A) high specific heat of oxygen and hydrogen atoms B) inability of water to dissipate heat into dry air D) absorption and release of heat when hydrogen bonds break and form E) fact that water is a poor heat ...

Biology
Why can carboxyl and phosphate groups act as acids?

Biology
General question: do polypeptides only make up proteins and not carbohydrates? and can they be formed by dehydration synthesis?

Physics
200

Chemistry
0.520 g

English
Need a good thesis statement about the gender protrayal in Jane Eyre. This is what I ahve, but looking for other suggestions: The patriarchal society of the Victorian Era causes Jane to struggle to become independent and to prove that men and women are both animated by the ...

alg.
solve the system by addition: -5x-9y = -5 x+5y=-15 I've tried this one over and over, but I can't seem to get the right answer. I don't even really know where to start. each time i try to do it, i go about it a little differently and i'm completely lost, pls ...

ENGLISH
DOES ANYONE HAVE A WEBSITE TO LOOK UP BOOKS? PLEZ HELP! Here is a good one: http://www.gutenberg.net Be aware, though, that not all books are available online. If the book is still under copyright, it's unlikely to find it or study guides for it online. =)

1. Pages:
2. <<Prev
3. 1
4. 2
5. 3
6. 4
7. 5
8. 6
9. 7
10. 8
11. 9
12. 10
13. 11
14. Next>>