Sunday

October 23, 2016
Total # Posts: 465

**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 don't 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 don't 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**

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*

**Human Anatomy**

What are the bony landmarks of the abdominopelvic cavity?

*January 13, 2009*

**French**

My french teacher has asked us too gather us questions to ask our pen pals on a live link up. (webcam to each other) but, i cannot think of anything to ask her. Please help and give me some ideas ? Charlie. x (:

*January 12, 2009*

**Atomic Mass**

Hi if I divide a molar mass of an element by Avogadro's number (63022X10^23) will i have the mass of 1 atom of the element? Thanks

*January 7, 2009*

**physics**

Spotted! Thanks Dr Bob.

*January 7, 2009*

**physics**

Hi if I divide a molar mass of an element by Avogadro's number (63022X10^23) will i have the mass of 1 atom of the element? Thanks

*January 7, 2009*

**Physics ideal gases**

Thank you both.

*January 3, 2009*

**Physics ideal gases**

If 2 samples of nitrogen (different PVTs) are separated by a conductive barrier, they will eventually achieve equilibrium, I believe. Am I right to assume that the final T and P at equilibrium in this case would be the SAME T and P if the barrier was highly insulated, then ...

*January 3, 2009*

**Physics ideal gases**

Thanks Damon, I realise I didn't tell you what i'm asked to do! I note your point about the start point for the equation. Thanks

*January 2, 2009*

**Physics ideal gases**

Would someone check my thinking please. PVT of an ideal gas (nitrogen) are all given. I've used PV=nRT rearranged to get the number of moles. Then, U= 3/2nRT to get the internal energy of the sample. Am I on the right track? Thanks.

*January 2, 2009*

**Physics**

For a child's swing in lightly damped SHM, I am given the time period and a value for g; (as well as the mass.) with just these, can i rearrange the equation: T (4s)= 2pi times sqrt l/g to calculate the length of the swing? I believe i have (3.98m), but the question says ...

*December 16, 2008*

**Physics**

For a child's swing in lightly damped SHM, I am given the time period and a value for g; (as well as the mass.) with just these, can i rearrange the equation: T (4s)= 2pi times sqrt l/g to calculate the length of the swing? I believe i have (3.98m), but the question says ...

*December 16, 2008*

**Physics (checking my thinking)**

Thanks both, for the answers.

*December 14, 2008*

**Physics (checking my thinking)**

Yes, it's zero. That seems to make the second term (m2u2) zero, but I still get what i think is the correct answer. What should be my next approach?

*December 14, 2008*

**Physics (checking my thinking)**

2 spheres, of unequal masses, hang on strings and are touching. Sphere a is pulled back to the left, string taught, and released, hitting sphere B at a known velocity. Sphere B's post impact velocity is known, and to the right. i have to find A's post collision ...

*December 14, 2008*

**physics**

How large a pressure increase (in ATM) must be applied to water if it is to be compressed in volume by 1%? The bulk modulus of water is 2 ~ 10^9 N/m^2 and 1 ATM = 10^5 N/m^2 I think that it is P = bulk modulus * 0.01 because 1/100 = 0.01, which is 1% of a volume. B = &#...

*December 10, 2008*

**Physics**

why 0.001? 1/100 is 0.01. I thought that was 1 %. Also is that pressure minus (-) or pressure (equals)?

*December 10, 2008*

**Physics**

How large a pressure increase (in ATM) must be applied to water if it is to be compressed in volume by 1%? The bulk modulus of water is 2 × 109 N/m2 and 1 ATM = 105 N/m2

*December 10, 2008*

**Physics**

Thanks very much, I appreciate it.

*December 5, 2008*

**Physics**

A pendulum of a given mass is pulled back through a given vertical height and released to swing back down to a 'wall' where it impacts. Can i use mg delta h to get E kin; and then use E= half mv^2 to get the collision impact velocity? Would someone check my thinking ...

*December 5, 2008*

**Physics, Collisions**

A pendulum of a given mass is pulled back through a given vertical height and released to swing back down to a 'wall' where it impacts. Can i use mg delta h to get E kin; and then use E= half mv^2 to get the collision impact velocity? Would someone check my thinking ...

*December 4, 2008*

**Geography**

Wouldn't the ground soak up the water? The sediment would come from the surrounding mountains.

*November 19, 2008*

**Geography**

I think sediment would build up on the valley floor and raise the elevation. And a lot more vegetation would grow. Am I close?

*November 19, 2008*

**Geography**

If Death Valley was located in an area with a lot of rainfall, how would the valley floor change? How would Death Valley change? Thanks!

*November 19, 2008*

**Geology/Glaciers**

Why do north facing slopes on mountains support glaciers today while south facing slopes do not?

*November 12, 2008*

**Physics SHM**

Sorry Bob, The wave represents a simple pendulum. In 3, I'm referring to the equation x(t)=Asin(wt+(greek letter phi)), so was looking to confirm that in that specific circumstance I outlined, the value of phi would either be zero or pi (as in 22/7). Thanks.

*November 5, 2008*

**Physics SHM**

Am self studying SHM, so sorry for the elementary questions. Would someone check/confirm some facts i think I've learned please. 1 If a sine wave graph starts at the origin at time = 0s, the sysyem is in equilibrium? 2 The amplitude at t= 0s is zero. 3 Same system, the ...

*November 5, 2008*

**Physics SHM**

Whether or not it'll help me, am i safe to deduce that: If a simple pendulum is released from rest at time t=0; from a displacement of x rad from equilibrium; Then the amplitude of the oscilation is also x rad? Thanks

*November 3, 2008*

**math**

what is the rest of the problem?

*October 13, 2008*