Sunday

November 29, 2015
Total # Posts: 414

**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*

**Physics**

If a space station must "provide one sixth the magnitude of the acceleration due to gravity on Earth" Can I use 9.81ms^-2/6 or is that too simple? Thanks.
*October 9, 2008*

**Physics/mechanics**

Thank you very much
*October 1, 2008*

**Physics/mechanics**

I have to do calculations based upon a bow shooting an arrow vertically, and I have to state any assumptions i'm making. Am I right to cite air resistance as negligible; and that the displacement will start 2m above the ground (not at ground level)? The rest I'm ok with.
*October 1, 2008*

**physics**

While her kid brother is on a wooden horse at the edge of a merry-go-round, Sheila rides her bicycle parallel to its edge. The wooden horses have a tangential speed of 6 m/s. Sheila rides at 4 m/s. The radius of the merry-go-round is 8 m. At what time intervals does Sheila ...
*September 29, 2008*

**Math**

I posted another question accidentally as an answer to my question
*September 12, 2008*

**Math**

I looked at that sight and can see the tables but what I have is a table that show the heights of students in a class males on top females on bottom with heights out beside them. I have to make a cumulative frequency table from the data in my collumns I have, height,frequency ...
*September 12, 2008*

**Math**

How do you make a cumulative frequency table
*September 12, 2008*

**college**

what's the most commonly overlooked reason for forgetting?
*September 9, 2008*

**GEOGRAPHY**

please could someone help, i need to find information about broughton chester airbus to write an essay about it.i need to write about what is made there how the parts are transported to different places how big the factory is what alterations have been made to the factory. ...
*May 19, 2008*

**CHEMISTRY**

I'm struggling with this homework question...i have no idea how to set this up. We start with a 33.50 mL aliquot of acetic acid and titrate it with 0.215 M of NaOH. Find the pH at: 21.7 ML added the equivalence point i don't understand how this works. please help, ...
*May 18, 2008*

**Physics**

A spring of k=11 N/m has a block of mass 4 kg attached to it on a frictionless table. If the block is pulled a distance 0.15 m to the right and released from rest, how long will it take the block to return to its equilibrium position?
*April 28, 2008*

**Physics**

The position of some object moving along the x-axis is observed to be x(t)=9cos(pi*t/3+pi/4) meters. Find the frequency.
*April 28, 2008*

**French Pen-Pal**

Me and my french pen pal enjoy chatting about our opinions of things. Maybe one of her favourite films (?) are on of the worst in your opinion. So tell her your own opinion. We also like talking about what's in our town (where we live) and what we love to do on the weekend...
*April 20, 2008*

**Algebra**

How do you convert money to pecent?
*April 8, 2008*

**chem**

Dude, That is a freakin HAAAAARRRDDD guestion. your in colledge right??
*April 7, 2008*

**Science**

MRIs use very powerful electo magnets>
*April 7, 2008*

**Physics**

I'm still not getting the right answer. It asks to convert it to centimeters but even when I do that I am still getting it wrong.
*April 6, 2008*

**Physics**

An advertisement claims that a centrifuge can produce a radial acceleration of 3,524g at 4,608 rev/min. Calculate the required radius of the centrifuge.
*April 6, 2008*

**Physics**

An object of mass 3.5x1023kg circles the earth and is attracted to it with a force whose magnitude is given be GMeM/r^2. If the period of rotation is 22 days, what is the distance from the earth to the object? Here G=6.67x10-11 Nm2/kg2, Me=6x1024 kg.
*April 5, 2008*

**Physics**

Suppose you are driving a car around in a circle of radius 157 ft, at a velocity which has the constant magnitude of 42 ft/s. A string hangs from the ceiling of the car with a mass of 1.8 kg suspended from it. What angle (in degrees) will the string make with the vertical?
*April 5, 2008*

**Physics**

A cannon shoots a shell straight up. It reaches its maximum height, 837 feet, and splits into two pieces, one weighing 2 lb and the other 5 lb. The two pieces are observed to strike the ground simultaneously. The 5 lb piece hits the ground 1,564 feet away from the explosion (...
*March 29, 2008*

**Physics**

OK thanks. There is another part of the question that asks for the momentum of the 4 lb piece and I can't figure out how to solve that.
*March 29, 2008*

**Physics**

A cannon shoots a shell straight up. It reaches its maximum height, 1,051 feet, and splits into two pieces, one weighing 2 lb and the other 4 lb. The two pieces are observed to strike the ground simultaneously. The 4 lb piece hist the ground 1,608 feet away from the explosion...
*March 29, 2008*

**Physics**

sorry I don't know what happened but I posted it again and the question is on there.
*March 29, 2008*

**Physics**

A cannon shoots a shell straight up. It reaches its maximum height, 1,051 feet, and splits into two pieces, one weighing 2 lb and the other 4 lb. The two pieces are observed to strike the ground simultaneously. The 4 lb piece hist the ground 1,608 feet away from the explosion...
*March 29, 2008*

**Physics**

You are stranded in the middle of a frozen pond, 825 m in diameter which is so slippery that your feet slide freely and don't move you. In desperation you write an S.O.S. on your hat, mass 0.6 kg, and fling it towards the north with a velocity of 13 m/s at 54o with the ...
*March 28, 2008*

**english**

which is correct?"What a disaster,"shouted Maria. "What a disaster!"shouted Maria!
*March 27, 2008*

**Physics**

A movie stunt man (mass 82.3 kg) stands on a window ledge 5.69 m above the floor. Grabbing a rope attached to a chandelier, he swings down to grapple with the movie’s villain (mass 72.3 kg), who is standing directly under the chandelier. (Assume that the stunt man’s ...
*March 13, 2008*

**Physics**

Ice-hockey star Wayne Gretzky is skating at 12.7 m/s toward a defender, who in turn is skating at 5.39 m/s toward Gretzky. Gretzky’s weight is 677 N; that of the defender is 869 N. Immediately after the collision, Gretzky is moving at 2.21 m/s in his original direction. ...
*March 13, 2008*

**Math**

Find a third-degree polynomial Q such that Q(1)=0, Q'(1)=0, Q''(1)=2, and Q'''(1)=12.
*February 29, 2008*

**Physics**

An engine is used to pull a train of two cars out of a mine. The floor slopes upward at an angle of 24o. Each car has a mass of 0.8x104 Kg and normally travels without friction on the tracks. The engine can exert a maximum force of 1.4x105 N on car A. If the engineer again ...
*February 24, 2008*

**Chemistry**

N2H4(g) + H2(g) 2 NH3(g) H1 = –1876 kJ 3 H2(g) + N2(g) 2 NH3(g) H2 = –922 kJ The H f for the formation of hydrazine: 2 H2(g) + N2(g) N2H4(g) will be
*February 22, 2008*

**science**

what are 3 types of symbiosis
*February 15, 2008*

**Physics**

Thank you so much.
*February 8, 2008*

**Physics**

A 10,000N car comes to a bridge during a storm and finds the bridge washed out. The 650-N driver must get to the other side, so he decides to try leaping it with his car. The side the car is on is 16.6 m above the river, while the opposite side is a mere 7.90 m above the river...
*February 8, 2008*

**english**

in to kill a mocking bird who leaves their shoes at the school??? who does scout escort home?? whoes education does atticus help finance and who urges scout to stand up out of respect for atticus???
*January 28, 2008*

**math**

You can always dig up an extra player
*December 16, 2007*

**math**

a bathtub can be filled by the hot and cold water pipes in four minutes and, when full, can be emptied by the waste pipe in five minutes. If it is half full and all three pipes are set running, when will the tub be filled?
*October 25, 2007*

**business studies**

I was wondering could anyone help me with question 6 an page 302 of the Business Studies for households and enterprises Junior Certificate by Matt Hynes
*October 13, 2007*

**CHEM**

A 5.00 g sample of Al pellets (specific heat = .89 J/g degrees c) and a 10.00 g sample of Fe pellets (specific heat = .45 J/g degrees c) are heated to 100.0 degrees C. The mixture of hot Fe and Al is then dropped into 97.3 g of water at 22.0 degrees C. Calculate the final temp...
*October 1, 2007*

**Chemistry**

i don't even understand what the problem is asking.
*October 1, 2007*

**CHEM**

A 5.00 g sample of Al pellets (specific heat = .89 J/g degrees c) and a 10.00 g sample of Fe pellets (specific heat = .45 J/g degrees c) are heated to 100.0 degrees C. The mixture of hot Fe and Al is then dropped into 97.3 g of water at 22.0 degrees C. Calculate the final temp...
*October 1, 2007*

**physics**

why are the lengths of days in spring and autumn the same? if the sun does not set, why is it so cold?
*September 21, 2007*

**One for Drwls (calc)**

Thanks bob, and thanks to drwls too, in the earlier ones. Charlie.
*September 15, 2007*

**One for Drwls (calc)**

Sorry, you're so quick, I took one of your answers for another question! Finally, Therefore, given my scenario, I could use the integral to calculate the area under the curve described by the derivative? Charlie.
*September 15, 2007*

**Calculus**

Great, and thank you very much. Charlie.
*September 15, 2007*

**Calculus**

"My reasoning is that 'undoing' the derivative gives me the derivative." oops, meant to write ......gives me the integral.
*September 15, 2007*

**Calculus**

Thanks- that was quick! Therefore, given my scenario, I could use the integral to calculate the area under the curve described by the derivative? Charlie.
*September 15, 2007*

**Calculus**

If I have a function f(x), and am given its derivative, f'(x): may I take it as a given that f(x) is an integral of f'(x). My reasoning is that 'undoing' the derivative gives me the derivative. Eg is 1/3x^3 an integral of x^2? Thanks.
*September 15, 2007*

**english**

complete subject and simple subject of this sentence. Ties in fancy boxes are gifts for some valentines.
*September 11, 2007*

**english**

complete subject and simple subject of this sentence. They can be funny or serious.
*September 11, 2007*