Friday

December 19, 2014

December 19, 2014

Total # Posts: 392

**Physics, relativity**

Thanks Drwls, but that's the press release I spotted the error in. I think!
*October 11, 2010*

**Physics, relativity**

I read this in a write-up of an experiment using atomic clocks: To reveal these effects, required the use of highly accurate atomic clocks, calibrated to check that they are perfectly in sync with each other – ticking down the nanoseconds (that's one billionth of a ...
*October 11, 2010*

**college chemistry**

whats is the boiling point of a solution composed of 17.6g of urea in (NH2)2CO in .300 kg of water
*October 4, 2010*

**physics**

the passenger's weight is ALWAYS mass x acceleration. Can you work out the acceleration at all 3 stages? The mass of the person is the same for all 3.
*September 28, 2010*

**11th grade**

Suppose you surveyed 50 students and 34 said that they approve of how the president is doing. Construct 90%, 95%, and 99% confidence intervals for the true proportion of students in your school who approve of how the president is doing. Be sure to specifically calculate the ...
*September 12, 2010*

**college physics**

A box on a frictionless horizontal surface is pulled by a tension of 42.4N directed at 45 degrees above the horizontal. what is the work done on the box as it moves 2.50 meters along the surface?
*September 11, 2010*

**college physics**

A box on a frictionless surface is pulled back a distance x into a spring with spring constant k and released. What is the formula for the kinetic energy of the box after it leaves the spring?
*September 11, 2010*

**College Physics**

A 50 kg skater moving at 5 m/s over frictionless ice grabs a rope stretched out 10m from a post and perpendicular to her path. She then moves in circles, spiraling inward as the rope wraps around the post. How fast is she moving when she is 2 meters from the post?
*September 11, 2010*

**8th grade Math**

3p - 1.5
*September 9, 2010*

**math**

let me retype the question. Sorry for the scribble. 1/2 X 1/2 answer in simplest form. must show work. thanks
*August 29, 2010*

**math**

desperately seeking help. work must be shown. answer must be in simplest form. Thanks 1 1 _ X _ 2 2
*August 29, 2010*

**mat115**

There are multiple choices for the answer to this problem. They are a) 1/5 b) undefined c) 5 d) 5/7 Thanks again for both of your help
*August 29, 2010*

**mat115**

Sorry Reiny, The question is 11-6/7-7 I thought the answer was 5/0= undefined. Can you please let me know if I am wrong and show the work so I can further understand your answer. Thanks Reiny
*August 29, 2010*

**Math**

Thanks Reiny, Yes, I spotted that it dosen't work for any run of primes, but it does up to 9. I'm afraid i don't really follow your explanation! An answer for dummies maybe? Charlie
*July 30, 2010*

**Math**

I have to find the relationship between these sequences, and express a generality. Could you help please. 1 + 3 + 5 + 3 + 1 = 3^2 + 2^2 1 + 3 + 5 + 7 + 9 + 7 + 5+ 3 + 1 = 5^2 + 4^2 1 + 3 + 1 = 2^2 + 1^2 I'm thinking sum of consecutive primes can be expressed in squares? ...
*July 30, 2010*

**Physics**

It's too hard. You should give up now
*July 6, 2010*

**gen.science**

A compound containing 3 atoms of carbon and 8 atoms of hydrogen is combined in a reaction with oxygen molecules. The two end products of this equation are carbon dioxide and water. Which chemical or element will have the largest number of moecules?
*June 21, 2010*

**chemistry**

What was the purpose of the phenolphthalein?
*June 1, 2010*

**Math algebra**

I'm reposting this, because Mathmate's answer hasn't directed me to the WHY? part of the question. Any prompts appreciated. The product of any two (whole) numbers each of which leave a remainder of 1 on dividing by 7, also leaves a remainder of 1 on dividing by 7...
*May 3, 2010*

**math**

I have this question to work on, and I don't know where to start investigating the answer: The product of any two (whole) numbers each of which leave a remainder of 1 on dividing by 7, also leaves a remainder of 1 on dividing by 7. Why? I THINK that I can see a quadratic ...
*May 2, 2010*

**physics**

If the angular quantities θ,ω,α were specified in terms of degrees rather than radians, how would the kinematics equations for uniformly accelerated rotational motion have to be altered?
*April 11, 2010*

**Physics**

Ok thanks, but why isn't this true for an arm or leg?
*February 3, 2010*

**Physics**

Why is the CM of a 1.00m length of pipe at its midpoint, whereas this is not true for your arm or leg?
*February 3, 2010*

**Math**

I need to figure out what a deposit of 3500 a month, with 9 percent intrest compounded monthly, would be in 6 years. Any help would be greatly appreciated.
*January 13, 2010*

**Math**

I need to figure out what a deposit of 3500 a month, with 9 percent intrest compounded monthly, would be in 6 years. Any help would be greatly appreciated.
*January 13, 2010*

**math**

-3/4
*January 13, 2010*

**freedom**

iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiissssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss WAR.
*January 11, 2010*

**Biology**

What differences would you expect to see in a population made up of individuals whose chromosomes experience crossing-over frequently compared with a population made up of individuals whose chromosomes do not cross over?
*January 6, 2010*

**algebra**

x+12+x-5+x=40 3x+7=40 3x=33 x=11 x-5+6 x+12=23 23, 11, 6
*December 16, 2009*

**AP Physics B**

can u give me these in numbers please, i dont understand what formulas u wrote and what some of the stuff in ur formulas are
*December 16, 2009*

**AP Physics B**

i figured out the amplitude and the period, i just dont kno how to get to the other 4 with using simple harmonic motion equations
*December 16, 2009*

**AP Physics B**

The position of a 20 g oscillating mass is given by x(t) = (2.0 cm) cos(2t), where t is in seconds. Determine the following. The Amplitude (cm.) The Period (s.) The Spring Constant (N/m) The maximum speed (cm/s) The total energy (J) The velocity at t=0.40 s. (cm/s) I need your...
*December 16, 2009*

**Chemistry**

The titration of 25.0 mL of an unknown concentration H2SO4 solution requires 83.6 mL of 0.12 M LiOH solution. What is the concentration of the H2SO4 solution (in M)? A) 0.40 M B) 0.10 M C) 0.20 M D) 0.25 M E) 0.36 M The answer is supposedly C, but I got A. What am I doing ...
*December 8, 2009*

**Chemistry**

Uranium-235 can be separated from U-238 by fluorinating the uranium to form UF6 (which is a gas) and then taking advantage of the different rates of effusion and diffusion for compounds containing the two isotopes. Calculate the ratio of effusion rates for 238UF6 and 235UF6 ...
*December 7, 2009*

**Chemistry**

Thanks so much! I got 4.82 which seems to be correct. Thank you again
*December 7, 2009*

**Chemistry**

Consider the following reaction: 2NiO (s)--> 2Ni(s) + 2O2 (g) If O2 is collected over water at 40.0 C and a total pressure of 752 mmHg, what volume of gas will be collected for the complete reaction of 25.67 g of NiO? I am struggling to set up this problem. Can anyone help ...
*December 7, 2009*

**Physical Science**

What is cracking and reforming? For what purposes are either or both used by the petroleum industry
*September 29, 2009*

**Physics**

I'm not doing the measuring, it's a graphing exercise, and I've been given the table of data. I was looking for confirmation of my choice of axes. But your extra points are well taken. Thanks for your comment.
*August 10, 2009*

**Physics**

I have to plot a graph of Pressure gradient vs average velocity (water in a pipe, I have all the data). I plan to put the average velocity on the x axis, since I could control that better in an experiment. Do you agree/ Thanks. Charlie
*August 10, 2009*

**english (help please)**

help
*August 2, 2009*

**english**

this is the quesion List four things to look for when you’re proofreading?
*August 2, 2009*

**english**

If you’re asked to list for things can the way of your listing be vertical or horizon.
*August 2, 2009*

**Physics**

Would someone check this please? A circular loop of wire of radius 0.10 m and of resistance 2.0 x 10^−3 ohms is in a region where there is a uniform magnetic field B. The field is at 30deg to the normal to the plane of the wire loop as shown in Figure 3. The magnitude of...
*June 20, 2009*

**physics**

The last stage in the fusion of hydrogen to form helium in the Sun involves the formation of an alpha particle (4He) from two 3He nuclei: 3He + 3He 4He + p + p The binding energy for 3He is 2.57 MeV per nucleon and that for 4He is 7.07 MeV per nucleon. Calculate the amount of ...
*June 19, 2009*

**Physics**

Would someone check this please? A circular loop of wire of radius 0.10 m and of resistance 2.0 x 10^−3 ohms is in a region where there is a uniform magnetic field B. The field is at 30deg to the normal to the plane of the wire loop as shown in Figure 3. The magnitude of...
*June 19, 2009*

**Physics**

The last stage in the fusion of hydrogen to form helium in the Sun involves the formation of an ƒ¿-particle (4He) from two 3He nuclei: 3He + 3He ¨ 4He + p + p The binding energy for 3He is 2.57 MeV per nucleon and that for 4He is 7.07 MeV per nucleon. ...
*June 18, 2009*

**Physics**

Would someone check this please? A circular loop of wire of radius 0.10 m and of resistance 2.0 ~ 10−3 ƒ¶ is in a region where there is a uniform magnetic field B. The field is at 30‹ to the normal to the plane of the wire loop as shown in ...
*June 18, 2009*

**Physics**

In an elastic collision: mass a is 1kg, and is moving at 100ms^1 in the +ve x direction when it hits mass b, 10kgs at rest. Given: mass a moves off at 80 ms^1 in the -ve x direction. What's the final velocity of mass b. Using cons of momentum, i say 2 ms^1 in the +ve x ...
*June 16, 2009*

**physics**

Thanks for that. So it would take longer to stop then?
*June 15, 2009*

**physics**

Would someone check my thinking please. A solid sphere (mass, r, and moment of inertia given) is rotating at a given angular speed. Friction is constantly applied at the 'equator' of the sphere, and brings it to rest in 3s. Find the force. I worked out the torque, and ...
*June 15, 2009*

**Physics/Maths**

Thanks
*June 11, 2009*

**Physics/Maths**

Keplers third law I understand. T^2/a^3 of one planet = T^2/a^3 second planet. But I can't do the algebra to solve for the second planet's a^3 (semimajor axis) Would someone walk me through the steps please? Thanks.
*June 11, 2009*

**Entropy**

Thanks for that.
*May 11, 2009*

**Entropy**

If a sample of an ideal gas is heated at a constant volume, I believe its entropy will increase. Am I right? Thanks.
*May 11, 2009*

**Physics capacitance**

Thank you very much.
*May 7, 2009*

**Physics capacitance**

I know that to solve: f=1 over 2 pi sqrt LC for C, I have to use C= 1 over L(2 pi f)^2 Can someone take me through the rearranging please. Thanks.
*May 7, 2009*

**Thermodynamics**

Thank you for giving such a detailed answer.
*May 3, 2009*

**Thermodynamics**

Would someone explain entropy in simple terms please. Thanks.
*May 3, 2009*

**physics :thinking check please**

HELP! Time running out! Thanks
*April 30, 2009*

**physics :thinking check please**

I think that: psi= A sin kx; is a solution to Schrodinger's time independent eqn for a particle confined: a) within an infinite pot well, and b) within the walls of a finite well;but psi= B exp(-kx) would only be a solution for outside the walls of a finite well. Am I ...
*April 30, 2009*

**Physics**

If energy is 1/2 mv^2; and m and v are always positive.... How come the ground state energy of Hydrogen is a minus value? Charlie
*April 14, 2009*

**physics**

Thanks, CI
*April 11, 2009*

**physics**

If I had made it conditional that the electron was orbiting at a constant radius, would it then be correct; and would it also be accurate in 'ordinary' situations, eg spinning a stone around on a string?
*April 11, 2009*

**physics**

I've just read that the centripetal force on an electron is mv^2/r; and that this is also equal to the electrostatic force pulling the electron toward the nucleus. Does mv^2/r hold good in all Newtonian siuations as a formula for centripetal force acting on a body? Thanks
*April 11, 2009*

**physics: relativity**

I think I can rearrange the Lorentz contraction equation, solving for v using: v=sqrt[1-(L/Lo)^2] x c^2 Would someone check my thinking please? Thanks
*March 30, 2009*

**math**

The answer was incorrect and that is why I am asking again Mr. Parsley
*March 27, 2009*

**math**

In the number 268,743 how many times greater than the 3 is the 6?
*March 27, 2009*

**math**

write the next four letters in this sequence A B Z Y C D
*March 27, 2009*

**Physics**

Reposted under Physics... I've tried for hours to solve for v, but can't get the rearranging right. I'm using L= Lo sqrt 1- v^2/c^2 Can anyone suggest the first couple of steps? I can get the answer by the way, by substituting values 'til I get the contracted ...
*March 27, 2009*

**lorentz contraction**

I've tried for hours to solve for v, but can't get the rearranging right. I'm using L= Lo sqrt 1- v^2/c^2 Can anyone suggest the first couple of steps? I can get the answer by the way, by substituting values 'til I get the contracted length. Original and final ...
*March 27, 2009*

**math**

what is the answer to. Write the next 4 letters in this sequence: A,B,Z,Y,C,D
*March 26, 2009*

**math**

In the number 268,743 how many times greater than the 3 is the 6
*March 26, 2009*

**lenses, still stuck!**

Thanks drwls, for that. However, the question acually asks me 2 things: the total M; and to find the length of the microscope! The questioner clearly thinks I have enough info to go on from what I've given above. Charlie
*March 24, 2009*

**lenses, still stuck!**

I need to calculate the magnification, m of an objective lens, so I can then x it by the eyepiece value for M to get the total magnification. I need v/u (v is dist from lens to image; u is dist of object to lens) I'm using 1/f = 1/v+1/u rearranged for 1/v. That's: 1/v...
*March 24, 2009*

**math**

Ms Writeacher my math work book which is a fifth grader Harcourt Math Practice Workbook does not say what Tues so my mon think it has to be the same Tues in the week of the other days
*March 9, 2009*

**math**

the response from Ms writeacher did not show the answer
*March 9, 2009*

**problem solving**

kirk grew a crystal in science class. On monday it was 13/16 inch tall. it had grown 1/4 inch bet friday and monday. It had grown 1/2 inch between Tues and Fri. How tall was Kirk'a crystal on Tues?
*March 9, 2009*

**math**

Thanks Jessica
*March 9, 2009*

**math**

what is the value of 4 in 0.045
*March 9, 2009*

**Physics**

Can the magnitude of a magnetic field be negative? If we consider an electron in a mag field, using r=mv/qB, the negative charge on the electron gives a negative answer. Do I drop the minus sign?
*February 25, 2009*

**Math/Physics**

In a 9V circuit, all the resistors are 20 or 40 kilo Ohms. Convention says that calcs should therefore be quoted to 1 sig fig, since the volts are the least accuracy. 2 seems better though. Any ideas?
*February 23, 2009*

**Sig Figs**

In a 9V circuit, all the resistors are 20 or 40 kilo Ohms. Convention says that calcs should therefore be quoted to 1 sig fig, since the volts are the least accuracy. 2 seems better though. Any ideas?
*February 22, 2009*

**Physics**

Thanks (I'm not much wiser!), but what's ve as in 'between ve and zero' please?
*February 17, 2009*

**Physics**

(1) 2 particles of equal mass are fixed at X=0 and another +ve point on the x axis. No other grav influences are in the system. (they can be ignored) I have to derive an expression for Vgrav at a general position x, on the x axis. I believe this is related to V=-GM/r, but can...
*February 17, 2009*

**gravitational potential**

(1) 2 particles of equal mass are fixed at X=0 and another +ve point on the x axis. No other grav influences are in the system. (they can be ignored) I have to derive an expression for Vgrav at a general position x, on the x axis. I believe this is related to V=-GM/r, but can...
*February 17, 2009*

**biology**

can i get some help here please? much appreciated.
*February 16, 2009*

**biology**

i'm doing the same problem and confused about the same thing, so i'll just wait for the answer
*February 16, 2009*

**Physics, Thinking check please**

Very kind drwls, thanks a lot. Charlie
*February 16, 2009*

**Physics, Thinking check please**

A 9v circuit charges a capacitor to steady state. Then the switch is opened. All resistance units in kilo-ohms: 2 rsistors, 20 and 40kO in parallel with a single 20 kO resistor. Total R is 3.33x10^4 Ohms. Am I close? If so, and the time constant is 1.6x10^-3 seconds, then is ...
*February 16, 2009*

**physics: Electricity/Resistance**

I forgot to say "take the reciprocal". Does that make more sense?
*February 16, 2009*

**physics: Electricity/Resistance**

I get it. My text shows your formula, but recommends 1/R= 1/R1+1/R2 etc as easier! I'm with you. If the numbers match, is my thinking ok?
*February 16, 2009*

**physics: Electricity/Resistance**

If I have a 9V circuit, with: 2 resistors in parallel; followed by: 2 single resistors in series; and I calculate the effective R of the parallel pair (using 1/R=1/R1+1/R2); can i then add this value to the series resistors to get a total for the circuit? As in: (1/R=1/R1+1/R2...
*February 16, 2009*

**Physics**

that's 3x10^6, not -6
*February 7, 2009*

**Physics**

I need to calculate the closest two parallel plates can get before they spark I have the voltage, and will use E=V/dist (rearranged) to get the distance. I THINK the field strength value I should use is 3x10^-6 Vm^-1. No other info is given in the question, so am i close? Thanks
*February 7, 2009*

**Physics**

I'm stumped: So bringing it back to the top. Hope that's ok! 2 charges, Q1 and Q2, equal magnitude, but different signs (not assigned) lie on a line, x axis, a known distance apart. Segment p-q lies centrally on the line, distance apart is known. An electron is ...
*February 4, 2009*

**physics fields and charges**

Sorry, the field is said to be constant around the central segment pq, which is only 10 cm long.
*February 3, 2009*

**physics fields and charges**

I'm stumped: 2 charges, Q1 and Q2, equal magnitude, but different signs (not assigned) lie on a line, x axis, a known distance apart. Segment pq lies centrally on the line, distance apart is known. An electron is released at p from rest, and passes q at a given time later...
*February 3, 2009*

**physics, fluids**

Thanks, all 3.
*January 24, 2009*

**physics, fluids**

It's given that it is an ideal fluid, and I'm asked to explain the significance of the expressions. I se a relationship with 1/2mv squared and mgh, but can't explain it clearly.
*January 24, 2009*

**physics, fluids**

would I be correct if I explained the 3 expressions in Bernoulli's equation as representing: P is the pressure 1/2*rho*v squared is the kinetic energy rho*g*h is the gravitational kinetic energy. Or is it more complicate than that. Thanks
*January 24, 2009*

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