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October 22, 2014

Posts by DrWLS


Total # Posts: 27,207

math
and she used the money for trip to africa
August 1, 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 for the third. So 9*9*8...
August 23, 2013

geometry
I WON A CAR!!!
August 23, 2013

geometry
Where is the road sign? What does Roseville have to d o with it?
August 23, 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)
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
August 6, 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 an area a*pi*a + 2 pi...
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.
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
August 3, 2013

Physics Normal force
Yes. The "normal" force is the perpendicular component. There can be a parallel component as well.
August 3, 2013

physics
20 kg wt = 200 Newtons Force Component along ground = 200*cos 60 = 100 N Work = 20 * 100 = 200 J
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
August 1, 2013

iinterpersonal comminication skills
I agree
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?
July 27, 2013

scince
The time interval doesn't matter. F = (0.060 kg/s)(15 m/s) = 0.90 N
July 26, 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.
July 26, 2013

MAT LAB
unanswered You have used 0 of 4 submissions
July 26, 2013

General Physics
The kinetic energy does not change. What does that tell you?
July 26, 2013

science
frequency = 600 Hertz (beats per second) Wavelength = (speed of sound)/(frequency) = (340m/s)/600 (s^-1) = 0.57 m
July 26, 2013

physics
delta S = entropy change = 1.6*10^5*[1/293 - 1/T2] = 470 Solve for T2
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.
July 25, 2013

physics
What are the dimensions of the 2.05? Meters displacement?
July 24, 2013

earth
____ cubic meters, since r is in meters.
July 23, 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]
July 18, 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 10-8/2.82 x 10-8 = 0.61 R(Al) = 0.509 Ù
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
June 4, 2013

help physics very 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 potential at distance d ...
June 4, 2013

chemistry, not 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.
June 2, 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 plane's velocity ...
June 1, 2013

SCI/220 HUMAN NUTRITION
What questions?
May 31, 2013

math
3% gets compounded 20 times. 5000*(1.03)^20 = $9030.56
May 31, 2013

physics
Your numbers require units. That is one of the first lessons you ahould have learned about physics.
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.
May 31, 2013

physics
What kind of length unit is "hm"?
May 31, 2013

physics
Don't you mean 90 m/hr? I have never heard of a length unit abbreviated "hm"
May 31, 2013

Math Linear function help?
The slope of the line is m = (y2-y1)/(x2-x1) =(3-6)/(4-0) = -3/4 When x = 0, y = 6, so the y-intercept is 6. y = (-3/4)x + 6 is the equation you want.
May 31, 2013

Physics
The E-field 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.
May 31, 2013

Physics
what are the choices?
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 up, the answer is 1.8 m
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 ambient pressure from that ...
May 30, 2013

Chemistry
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
May 29, 2013

Physics
Write an equation for the E-field along the line joining the two charges. Let the position of the charge be x. Set the E-field 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 other. E = k*[(5.0*10...
May 29, 2013

physics
(average velocity)*(time) = 23.9 m/s*12 s = 286.8 m
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.
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 small-scale vorticity and turbulence in the water. A large fraction of the ocean wave energy will also be reflected by the dock.
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^(n-1) = 3n*(3x+2)^(n-1) 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^(m-1) Add the two terms d/dx [(3x+2)^n +(2x+3)^m] = 3n*(3x+2)^(n-1) + 2m*(2x+3)^(m-1)
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 location is quite near the...
May 29, 2013

science
"Plaastids" is misspelled. You will have to write your own poem. This may help: http://www.readwritethink.org/files/resources/interactives/acrostic/
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
May 29, 2013

MATH
One row of five posts across from the stream. Two rows of four perpendicular to the stream. Total = 13
May 29, 2013

language (sentence fluency)
D. is most fluent
May 28, 2013

Physics
The sum of the individual resistances: 15.0 ohms. You do not need the battery voltage for that question.
May 28, 2013

physics
Speed is constant and direction is not changing. Therefore acceleration is zero.
May 28, 2013

Geometry
You should rethink 4. 2. is 'sometimes'. Consider the isosceles case. 3. is true because of the law of sines
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.
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.
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.
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 ...
May 27, 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
May 27, 2013

algebra
(a) [f(3) - f(1)]/(3-1) = (28-4)/2 = 12 (b) [f(5) -f(3)]/(5-3) = (76-28)/2 = 24 (c) [f(4) - f(1)]/(4-1) = (your turn)
May 27, 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
May 27, 2013

middle madness
X - 15 - 8 -[(X-15-8)/2) = 46 (X-23)/2) = 46 X -23 = 92 X = 115
May 27, 2013

math
Your numbers require dimensions. Inches? Centimeters? Meters?
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 find a more...
May 26, 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.
May 26, 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
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.
May 25, 2013

algebra
If "diffance" means difference, the answer is 20. You don't need to use algebra.
May 24, 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
May 24, 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 j Divide than by the...
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 online.
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.
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 zero. That leaves you ...
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.
May 23, 2013

Physics : Young's Modulus
The effective spring constant of the string is k = Y*S/L Newtons/meter When the mass m is dropped from the fixed end, the string will stretch a maximum amount dL, so that m g L = (1/2) k *dL^2 = (1/2)Y*S/L*dL^2 dL^2 = 2 m g L^2/(Y*S) dL/L = sqrt[2 m g/(Y*S)] If the string is ...
May 23, 2013

math,science
cosa = -0.6 a = 126.87 degrees or 233.13 degrees Your requirement that 180<a<360 degrees requires you to pick the second value for a. Now calculate 3tana + 25sin^2a I get 4 + 16 = 20.
May 23, 2013

PHYSICS FINAL (orbital)
The satellite's mass doesn't matter. You will need to use the fact that the Earth's radius is 6371 km. The satellite is therefore 9921 km from the Earth's center. The value of the acceleration of gravity (g') there is g' = g*(6371/9921)^2 = 4.046 m/s^2 ...
May 22, 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
May 22, 2013

PHYSICS SATELLITE PROBLEM
See my answer to your same question posted later.
May 22, 2013

physics
Average speed = (134+108)/16.8 m/s Average velocity = 26/16.8 m/s
May 22, 2013

Physics
Are the batteries and resistors in parallel or series? It makes a difference. There is no "circuit below"
May 22, 2013

math
Let x be the number of oranges, y be the number of pears and z be the number of apples. y = 2 z y = x + 4 z = 6 (apples) All you have to do is substitute. y = 12 (pears) x = y-4 = 8 (oranges)
May 22, 2013

Physics
Have you read about Coulomb's law? If not, it's time you did. F = k*Q1*Q2/R^2 In your case, Q1 = -Q2 = 2.0*10^-6 Coulombs R = 5.0*10^-2 meters k is the "Coulomb constant", 8.99*10^9 N*m^2*/C^2 Solve for F in Newtons. The force will be attractive since the ...
May 22, 2013

probability
This problem is not about geometry You want the probability that Bret's last toss will exceed Shawn's by 11 or more. There are 20x20 = 400 possible outcomes of the two tosses. Here are some of the ways Bret can win ion the last toss. Bret can throw 12 while Shawn ...
May 22, 2013

Math Please Help
1/b = 1/50 - 1/a = (a-50)/50a b = 50a/(a-50) If a = 100, b = 5000/50 = 100 If a = 75, b = 150 There are no other integer a values ¡Üb that yield an integer for b. 50/(a-50) would have to be an integer
May 22, 2013

math i don't get it
There are two cups of food coloring per 16 gallons of lemonade. Please reread the answers with more care.
May 21, 2013

math i don't get it
There is one ounce of food coloring per gallon of lemonade. So... There are 16 ounces in 16 gallons. 16 ounces of food coloring are two cups. You need to use the fluid ounces to cups conversion factor: (8 fl. oz. per cup)
May 21, 2013

understanding angles
An angle and an angel are two different things. This would be a good time to learn the difference. If you cut a pie into 72 degree equal slices, you make a total of 360/72 = five pieces. Just how many pieces are left does not affect the answer. They only want to know how many ...
May 21, 2013

These are my last couple! Please Help In Math.
Your questions are incomplete and many contain unexplained symbols.
May 21, 2013

physics
-g = -9.8 m/s^2 The angle and the speed don't matter. Gravity provides the acceleration
May 19, 2013

physics
1050 N/C field strength means the same thing as 1050 Volts per meter voltage gradient between the plates. 1050*d = 30.3 Solve for plate separation d. d = 0.0289 m
May 19, 2013

Algebra
For the first part, use conservation of energy, and let Vo be the initial veloicty (Vo^2)/2 = gH Solve for maximum height H H = 240 m Time to reach maximum height = H/V(average) = 240/34.3 = 7.43 s
May 19, 2013

Physics
Tangential force = (tangential acceleration) x (mass) = (35/11)m/s^2*1100 = 3500 N Centripetal force at 15 m/s = (V^2/R)*(mass) = 15^2/500 x 1100 = 495 N (It continues to rise as the car accelerates)
May 19, 2013

Physics
Four times as much, 496 N, can be lifted. The mechanical advantage tells you that.
May 19, 2013

physics
60 mph = 88 ft/s = velocity change Acceleration = 88/10 = 8.8 ft/s^2 That is 0.27 g's.
May 18, 2013

Science
Yes. At equivalent distances from the magnets, stronger magnets have stronger B-fields.
May 17, 2013

German
..wir machen Fotos. So many commas would probably not be used.
May 17, 2013

math
Divide f(0) - f(-1) by the change in x. You have to know what the function f(x) is.
May 17, 2013

Physics
A free body diagram of forces acting on the ball should tell you that Tan 35 = (mg)/(mv^2/R) = R g/ v^2 The mass m cancels out. Solve for v.
May 16, 2013

physics
100 km/h = 27.78 m/s 60 km/h = 16.67 m/s (delta V) = V2 - V1 = 16.67-27.78 = -11.11 m/s acceleration = (V2 -V1)/t = -2.22 m/s^2
May 16, 2013

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