drwls
Most popular questions and responses by drwls
math
Derivatives are usually not taught in 5th grade. That is what your question is about: Rates of change. Complete the following statements with the correct words Note: Correct spelling is important. If s(t) is a distance (or height or position) function,
asked on February 19, 2007 
calculus
We are not going to do that work for you, but will be glad to help you. The unit sphere is the sphere with radius 1 centered in the origin. They give you the coordinates of a vector. Compute the dot product of the vector and the local surface area normal
asked on August 5, 2007 
Physics
Equate the increase in potential energy at the higher elevation, M g H, to the decrease in kinetic energy. Make sure you include the kinetic energy of rotation, which is (1/2) I w^2. For a sphere of radius R, V = R w and I =(2/5) I R^2 Therefore
asked on March 21, 2007 
Integral
That's the same as the integral of sin^2 x dx. Use integration by parts. Let sin x = u and sin x dx = dv v = cos x du = cos x dx The integral is u v  integral of v du = sinx cosx + integral of cos^2 dx which can be rewritten integral of sin^2 x = sinx
asked on February 20, 2007 
note to those with unanswered physics questions
I have only been able to answer a few tonight. Preference is and will be given to questions in which evidence of work or thought is shown by the person posting the question.
asked on October 21, 2010 
US HISTORY
Bartolomeu Dias first rounded the Cape of Good Hope in 1488. Ten years later, Vasco da Gama also sailed around the Cape and continued to eastern Africa and India, claiming it for Portugal. Barthelomew Diaz
asked on August 20, 2005 
Math (Calculus 121)
The derivative tells you the slope at any point. df/dx = 8 x^3  12 x When x = 3, the slope is m = 8*27  36 = 180 and the equation of the tangent line is (y  228) = 180*(x  3) y = 180 x  540 + 228 = 180 x  312 wow, that was absolutely correct (i just
asked on February 19, 2007 
math,algebra
They may want you to add the fractions and give the answer in forms of a fraction. in that case, you need to convert to common denominators before addineg. In that case 1/3 + 1/5 + 1/10 = (10 + 6 + 3) /30 = 19/30 5/6  3/5 = (25  18)/30 = 7/30 You answer
asked on December 6, 2006 
Physics
The stored potential energy in the trampoline at maximum compression, (1/2) k X^2, equals the gravitational potential energy at maximum height, M g H. (Kinetic energy is zero in both cases) X = 0.5 m g = 9.8 m/s^2 H = 2.5 m k = the spring constant. Solve
asked on March 13, 2007 
chemistry
First of all, you need to know how many g of Mg actually reacted in the first reaction. You can determine this by determining the limiting reactant. The reaction is Mg + F2 > MgF2 16.2 g of Mg is 16.2/24.32 = 0.666 moles 25.3 g of F2 is 25.3/38.0 = 0.666
asked on August 30, 2005 
Math
Are you trying to solve for x, n or p? solve for n Show me how to work this problem. 2n = 4xp  6 what is the problem? what grade r u in i am in 6 grade To get n all by itself, you need to divide by 2. But if you divide by 2 on the left, you have to divide
asked on March 14, 2007 
MATH
24/(x+1) + 12/(4x) = 14 Multiply both sides by (4x)(x+1) 24(4x) + 12(x+1) = 14(4x)(x+1) 96  12x + 12 = 14(x^2 3x 4) = 14x^2 +42 x +56 Combine terms and solve for x. sorry guys, here's another.I'm not the greatest at math but i do know some... The
asked on January 17, 2007 
Chemistry
Some is released if the temperature is increased. Some O2 is always entering and leaving solution at the same time. You end up with an equilibrium between the two processes.
asked on June 21, 2005 
Briittany algebra question
You should have posted this as a new question, not as a comment to someone else's thread. > Just combine "x" terms and combine constants on separate sides of the equation x = 2 x = 2 x = 2
asked on December 1, 2008 
calc check
If that is the y value of the center of mass, I don't know why the factor (1/2) is there I also don't agree with your calculation of the x value, which should be 1/(ln 2). I agree with you that the area is ln 2 find the center of mass of the region bounded
asked on June 29, 2007 
math
The "x intercept" is where y = 0, which is where the curve crosses the x axis. Solve y = x^2+ 2x 8 = 0 You can write that as y = (x+4) (x2) = 0 There are two places where y = 0. The factored equation tells you where they are. how would I find the
asked on June 22, 2007 
math
This is a "trial and error" type question. Algebra alone won't help you. First see what you could do buying 19 cow brains ($95) with $5 left. That could get you ten sheep brains ($1) and two pig brains ($4). The total would be only 31 total. Not enough. So
asked on March 28, 2007 
math algebra
Do you want the equation of a line through that point (1,2) with slope m = 4? Use the equation (yy*) = m(x  x*) where x* and y* are the coordinates of the point the line has to pass through. (1,2)m=4
asked on March 3, 2007 
polynomials
No to both questions. A polynomial is a sum of at least one integer power of x (or other unknown), each multiplied by a constant. '9' is simply a constant. 2^x is a power of 2, not a power of x. Is 9 a polynomial? Is 2^x a polynomial?
asked on January 7, 2007 
math
I believe Lance meant to write x = 5/18 I am wondering why you have two minus signs before the number 13. Two minuses make a plus, but usually they are not written that way. combine like terms 18x=5 solve for x x=5/18 what does x equal in...
asked on January 17, 2007 
Math
(1 & 2) The first three points do not fall on a straight line, and there is no value of k that will make that happen. (4) To find the quadratic y = a x^2 + bx + c that passes through the first three points, solve simultaneously 1 = c 3 = 4a + 2b + c 6 = 16
asked on December 25, 2006 
Business Calculus
The indefinite integral, or which call the "antiderivative", of f'(x)=6x8x^3 is f(x) = 3x^2  2x^4 + C where C is any constant. Plug in x = 2 to that to see what C is. 3 = 3*4  2*16 + C Determine the antiderivative of the following function given the
asked on December 3, 2006

Physics
you're way smarter than I am.
posted on October 16, 2016 
physics
Use the inverse square law. You will need to look up the radius of the earth. It is about 3960 miles, as I recall. Square the ratio of the the distances to the center of the Earth at the top and the bottom of the building. Use that factor to compute the
posted on June 14, 2016 
4th grade math
oh wow, crazy teacher huh? well it means to just multiply it
posted on August 7, 2014 
math
and she used the money for trip to africa
posted on August 7, 2014 
Math
Already answered. math  MathMate, Saturday, May 28, 2011 at 11:00pm Here we have 10 digits, of which the first one cannot be zero. If the three digits are distinct, there are 9 choices for the first digit, still 9 (including zero) for the second, and 8
posted on August 23, 2013 
geometry
Where is the road sign? What does Roseville have to d o with it?
posted on August 23, 2013 
physical science
A balance measures mass. A graduated cylinder measures the volume of liquids.
posted on August 7, 2013 
Trig
a. If you are only given the value of ƒÆ , you cannot deduce the value of the radius r. b. ƒÆ = pi  0.213 rad = 2.929 rad csc ƒÆ = 4.739 c. cos ƒÆ = 0.977 d. cot ƒÆ = 1/(tan ƒÆ )=  (8/(ã3)
posted on August 7, 2013 
Physics
If T is the half life in days (1.6)/2.0 = (T/156)^(1/2) 0.8 = 0.08006 T^1/2 9.992 = T^1/2 T = 99.8 days The decay constant k is related to the half life by k = ln2/T
posted on August 7, 2013 
Science
Let the unit cube side be a. Its volume is a^3. Its area is 6a^2. The ratio is a/6. The inscribed sphere has a volume of (pi/6)a^3 and an area of pi*(a/2)^2*4 = pi a^2. The ratio is a/6. The inscribed right cylinder has a volume (pi/4)a^2*a = pi*a^3/4 and
posted on August 5, 2013 
math
N = 2^1 + 2^2! + 2^(1000!)!) The last number has no ending digits as small as 2 or 4 006 would be the last three digits of the complete number.
posted on August 4, 2013 
physics
Let the tension be T and the acceleration be a. Write separate free body diagram equations for the two weights T  100g*sin37 = 100 a 70 g  T = 70 a 170 a = 9.82 g a = 0.058 m/s^2 Now solve for T
posted on August 3, 2013 
Physics Normal force
Yes. The "normal" force is the perpendicular component. There can be a parallel component as well.
posted on August 3, 2013 
physics
20 kg wt = 200 Newtons Force Component along ground = 200*cos 60 = 100 N Work = 20 * 100 = 200 J
posted on August 2, 2013 
physics
For the speed of the car (V), solve V^2/R = 2 m/s^2 V = sqrt400 = 20 m/s The centripetal force is (acceleration)*(Mass) = 2*2500 = 5000 N Centrifugal acceleration is the opposite of centripetal acceleration
posted on August 2, 2013 
scince
The time interval doesn't matter. F = (0.060 kg/s)(15 m/s) = 0.90 N
posted on July 27, 2013 
iinterpersonal comminication skills
I agree
posted on July 27, 2013 
geometry
What is the meaning of P(6,6)? Is it the value of P(x,y) where x = y = 6? Is that 2/(3x) or (2/3)*x on the right?
posted on July 27, 2013 
MAT LAB
unanswered You have used 0 of 4 submissions
posted on July 27, 2013 
Physics
f = (1/2pi)*sqrt(k/M) Hz M = 1481 kg k = 81*9.8/0.015 = 52900 N/m f = 5.0 Hz.
posted on July 27, 2013 
General Physics
The kinetic energy does not change. What does that tell you?
posted on July 26, 2013 
physics
delta S = entropy change = 1.6*10^5*[1/293  1/T2] = 470 Solve for T2
posted on July 26, 2013 
science
frequency = 600 Hertz (beats per second) Wavelength = (speed of sound)/(frequency) = (340m/s)/600 (s^1) = 0.57 m
posted on July 26, 2013 
physics
What are the dimensions of the 2.05? Meters displacement?
posted on July 25, 2013 
math
You want to know Young's and the shear modulus, E and G, not Young's and shear modules. The equations you need can be found at http://silver.neep.wisc.edu/~lakes/PoissonIntro.html Your last sentence is incomplete.
posted on July 25, 2013 
earth
____ cubic meters, since r is in meters.
posted on July 24, 2013 
physics
Let ds be the density of steel in kg/liter. Let df be the average density of gasoline. You will need to look it up. Avg density = [2.6 + 15/df]/[2.6/ds + 15]
posted on July 19, 2013 
Physics
The ratio of the resistances will be the same as the ratio of the resistivities, if lengths and diameters are the same. R(Cu)/R(Al) = 1.72 x 108/2.82 x 108 = 0.61 R(Al) = 0.509 Ù
posted on June 5, 2013 
heeeeeeeeeeeelp physics vrey tough
Never mind the General Relativity approach I suggested. Time goes slower at the lower orbit because of Special relativity . Use the two different satellite speeds to deduse the time shift for one orbit. You want the extra credit.. so you do the numbers
posted on June 5, 2013 
heeeeeeeeeeeelp physics vrey tough
I assume you are being asked about the change in the rate of a clock in a gravitational field (of the sun, in thic case). There is a General Relativity formula for it. (Due to Schwarzschild, I believe) delta T = T*(delta V)/c*2 V is the gravitational
posted on June 4, 2013 
physics
What does the symbol h represent? The arrow from reactants to products? Here is one answer. 3 H2(g) + N2(g)> 2 NH3(g) The others are not hard. You need to try them yourself.
posted on June 3, 2013 
Physics
Plane mass increases by a factor of 2^3 = 8. Plane lift increases by a factor 2^2 = 4 Plane drag increases by an unknown factor between 1 and 2. Engine power will have to increase to compenstate for increased prssure drag and boundary layer friction. The
posted on June 2, 2013 
math
3% gets compounded 20 times. 5000*(1.03)^20 = $9030.56
posted on May 31, 2013 
SCI/220 HUMAN NUTRITION
What questions?
posted on May 31, 2013 
physics
What kind of length unit is "hm"?
posted on May 31, 2013 
physics
Don't you mean 90 m/hr? I have never heard of a length unit abbreviated "hm"
posted on May 31, 2013 
physics
How fast is it accelerating? You don't say. To get the power required, you need the kinetic energy at a later time, or the rate of acceleration.
posted on May 31, 2013 
physics
Your numbers require units. That is one of the first lessons you ahould have learned about physics.
posted on May 31, 2013 
Math Linear function help?
The slope of the line is m = (y2y1)/(x2x1) =(36)/(40) = 3/4 When x = 0, y = 6, so the yintercept is 6. y = (3/4)x + 6 is the equation you want.
posted on May 31, 2013 
Physics
The Efield in any direction is the rate of change of potential with distance along that direction. The a question contains the words"the following", you really must state what the choices are. And please stop changing names.
posted on May 31, 2013 
Physics
what are the choices?
posted on May 31, 2013 
physics
Recheck you numbers. Telescopes have long focal lengths and their eyepieces (if used) have short focal lengths. The telescope length, if you are using a refractor, is the sum of the objective and eyepiece focal lengths. Assuming you got the numbers mixed
posted on May 30, 2013 
physics
(average velocity)*(time) = 23.9 m/s*12 s = 286.8 m
posted on May 30, 2013 
Physics
Write an equation for the Efield along the line joining the two charges. Let the position of the charge be x. Set the Efield equal to zero and solve for x. You can assume that x has to be > 50 cm, so that the fields due to the two charges oppose each
posted on May 30, 2013 
Physics
At 60,000 Pa gauge pressure, the absolute pressure inside the ball is 101,325 + 60,000 = 161,325 Pa Dropping the absolute temperature from 293 to 283 K decreases the absolute pressure in the ball by a factor 283/293, resulting in 15,582 Pa. Subtract
posted on May 30, 2013 
Physics
What you have written in not a balanced chemical reaction. Where is the arrow (>) ? An arrow must separate the two sides of the reaction. What is h2? Cr2O3 is not a gas
posted on May 30, 2013 
science
"Plaastids" is misspelled. You will have to write your own poem. This may help: http://www.readwritethink.org/files/resources/interactives/acrostic/
posted on May 29, 2013 
Sam
No work is done, because the dock does not move. However, some of the kinetic energy of the wave will be converted to heat and smallscale vorticity and turbulence in the water. A large fraction of the ocean wave energy will also be reflected by the dock.
posted on May 29, 2013 
sam
Someone left out the word WORK in your question. The question should read: "How much Work do you do if you push a garbage can with a force of 30N while sliding it 4 meters" The answer is Work = Force x Distance, which is 120 Joules in this case.
posted on May 29, 2013 
language (sentence fluency)
D. is most fluent
posted on May 29, 2013 
Geometry
You should rethink 4. 2. is 'sometimes'. Consider the isosceles case. 3. is true because of the law of sines
posted on May 29, 2013 
maths
For d/dx (3x+2)^n, let u(x) = 3x + 2 f(u(x)^n)= u^n df/dx = (df/du)*(du/dx) = 3*n*u^(n1) = 3n*(3x+2)^(n1) For d/dx(2x+3)^m, Let v(x) = 2x +3 g(v(x)^m) = v^m dg/dx = (dg/dv)*(dv/dx) = 2 mv^(m1) Add the two terms d/dx [(3x+2)^n +(2x+3)^m] =
posted on May 29, 2013 
physics
Draw a free body diagram and set the total moment about the fulcrum/pivot equal to zero. Let x be the distance of the elder brother from the pivot. 80*x = 50*2 + 30*7 = 310 N*m x = 3.87 m (on the opposite side of the pivot from the 30 N brother) This
posted on May 29, 2013 
physics
Speed is constant and direction is not changing. Therefore acceleration is zero.
posted on May 29, 2013 
Physics
The sum of the individual resistances: 15.0 ohms. You do not need the battery voltage for that question.
posted on May 29, 2013 
MATH
One row of five posts across from the stream. Two rows of four perpendicular to the stream. Total = 13
posted on May 29, 2013 
science
250 ml of a 1.0 M glucose solution contains 0.25 moles of glucose. Each mole of glucose has a mass of 180 g. 0.25 x 180 = ___ g
posted on May 29, 2013 
algebra
(a) [f(3)  f(1)]/(31) = (284)/2 = 12 (b) [f(5) f(3)]/(53) = (7628)/2 = 24 (c) [f(4)  f(1)]/(41) = (your turn)
posted on May 28, 2013 
math
ab is not a fraction. It is a product. 56% = 14/25 14 and 25 are coprime numbers a and b. Their sum is a + b.
posted on May 28, 2013 
Physics
(a) +162 F = 90 C (b) 90 K Each 1.8 degree rise in deg F is a 1.0 degree rise in the C or Kelvin Temperature.
posted on May 28, 2013 
Physics
(a) 3 m/s is not an acceleration rate. You probably mean 3 m/s^2. (b) Weight = M*g = 490 N (c) 3 m/s is not a deceleration rate.
posted on May 28, 2013 
middle madness
X  15  8 [(X158)/2) = 46 (X23)/2) = 46 X 23 = 92 X = 115
posted on May 28, 2013 
science
Please be more careful with your spelling. A chemical reaction in which two or more substances undergo a chemical union to form a more complex substance is: a Direct Combination or Synthesis Reaction
posted on May 28, 2013 
Physics
It is four times the potential due to a charge at a single corner. Your equation 1/4¦Ð = 8.99 ¡Á 10^9 N ¡¤ m2/C2 is obviously incorrect. The distance from the center of the square to a corner is R = 1.414 m The potential due to a single corner charge
posted on May 28, 2013 
Physics
They have already told you that the velocity of the truck (less sand) remains the same. The momentum of the truck (less sand) therefore also stays the same.
posted on May 28, 2013 
Physics
The friction force in the reverse direction is 200*0.4 = 80 N. The net forward force acting on the box is therefore Fnet = 100  80 = 20 N Acceleration = Fnet/Mass = Fnet*g/(Weight) = 20*9.8/200 = 0.98 m/s^2
posted on May 27, 2013 
math
Your numbers require dimensions. Inches? Centimeters? Meters?
posted on May 27, 2013 
physics
The volume of the steel in the coil is V = Length*Width*Thickness = (mass)/(density) = 156 kg/7.9*10^3 kg/m^3 = 1.98*10^2 m^3 Length = 1.98*10^2/(0.5)(8*10^4) = 49.4 meters I have used an "average" density for steel. If you know the alloy type, you can
posted on May 27, 2013 
power dissipation
I = 40V/40,000 ohms = 10^3 A goes through each resistor, since they are in series. The power dissipated in R1 is I^2*R1 = 10^6*10,000 = 10^2 watts
posted on May 25, 2013 
PHYSICS
1. Use conservation of momentum. Let the initial direction of X be considered positive. 20  12 = 2 + (momentum of Y) Momentum of Y = 10 N*s 2. Momentum of Force*t = 20i + 70j (N*s) is added to the body Initial momentum = 5i 10j Final momentum = 25i + 60
posted on May 25, 2013 
algebra
If "diffance" means difference, the answer is 20. You don't need to use algebra.
posted on May 25, 2013 
physics
Convert all speeds to the same units and than compare them. For the bicycle, 18 km/h = 18000 m/3600 s = 5.0 m/s For the car 2 km /min = 2000 m/60 s = 33.3 m/s The athlete runs at 7 m/s. The bike is slowest and the car is fastest in this case.
posted on May 25, 2013 
science
Don't you mean Fe + 2HCl > FeCl2 + H2 ? 55g Fe is 0.984 moles 36.5 g HCl is 1.000 moles HCl is slightly in excess of stoichiomentric. 0.984 moles of HCl are evolved. That is 22 liters at STP
posted on May 24, 2013 
physics
The magnetic field B provides the centripetal force to keep it in a circular path. e V B = m V^2/R R = mV/(eB) m and e are the electron mass and charge. You don't need the Biot Savart Law for this question. There are plenty of good explanations of it
posted on May 23, 2013 
Physics
Are you talking about sound waves? You need the speed of wave propagation to answer the question. For sound in air, it is about 340 m/s. Wavelength = (Wave speed)/(Frequency) You do not need to make approximations for pi to do the calculation.
posted on May 23, 2013 
chem ! help its killing me to :/
This is not a service where long homework assignments are done for you. You have to make an effort. Learn and apply the ideal gas law.
posted on May 23, 2013 
Physics !!!!! HELP PLEASE
K.E. is (1/2) M V^2 To get it in Joules, M must be in kg. bullet KE = 960 Joules If motorcycle KE = 960 J,and its mass is 173 kg, (1/2)*173*Vm^2 = 960 then the motorcycle velocity is Vm = 3.33 m/s Convert that to km/h
posted on May 23, 2013 
physics
Use the principle of superposition. The E field at the center will be the sum of two cases: (a) +3 microC at the open corner, and all three other corners (b) 6 microC at the open corner location only Case (a) results in a net E field at the center of
posted on May 23, 2013