# drwls

Popular questions and responses by drwls
1. ## 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,

2. ## 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

3. ## 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.

4. ## 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

5. ## 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

6. ## 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

7. ## 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

8. ## 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

9. ## 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) (x-2) = 0 There are two places where y = 0. The factored equation tells you where they are. how would I find the

10. ## 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

11. ## 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

12. ## 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

13. ## math algebra

Do you want the equation of a line through that point (1,2) with slope m = 4? Use the equation (y-y*) = m(x - x*) where x* and y* are the coordinates of the point the line has to pass through. (1,2)m=4

14. ## 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

15. ## 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

16. ## 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...

17. ## MATH

24/(x+1) + 12/(4-x) = 14 Multiply both sides by (4-x)(x+1) 24(4-x) + 12(x+1) = 14(4-x)(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

18. ## 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?

19. ## 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

The indefinite integral, or which call the "antiderivative", of f'(x)=6x-8x^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

21. ## 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

22. ## 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.

1. ## Physics

you're way smarter than I am.

posted on October 16, 2016
2. ## 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

oh wow, crazy teacher huh? well it means to just multiply it

posted on August 7, 2014
4. ## math

and she used the money for trip to africa

posted on August 7, 2014
5. ## 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
6. ## geometry

Where is the road sign? What does Roseville have to d o with it?

posted on August 23, 2013
7. ## physical science

A balance measures mass. A graduated cylinder measures the volume of liquids.

posted on August 7, 2013
8. ## 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
9. ## 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
10. ## 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
11. ## 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
12. ## 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
13. ## Physics Normal force

Yes. The "normal" force is the perpendicular component. There can be a parallel component as well.

posted on August 3, 2013
14. ## 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
15. ## 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
16. ## scince

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

posted on July 27, 2013
17. ## iinterpersonal comminication skills

I agree

posted on July 27, 2013
18. ## 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
19. ## MAT LAB

unanswered You have used 0 of 4 submissions

posted on July 27, 2013
20. ## 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
21. ## General Physics

The kinetic energy does not change. What does that tell you?

posted on July 26, 2013
22. ## physics

delta S = entropy change = 1.6*10^5*[1/293 - 1/T2] = 470 Solve for T2

posted on July 26, 2013
23. ## 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
24. ## physics

What are the dimensions of the 2.05? Meters displacement?

posted on July 25, 2013
25. ## 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
26. ## earth

____ cubic meters, since r is in meters.

posted on July 24, 2013
27. ## 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
28. ## 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

posted on June 5, 2013
29. ## 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
30. ## 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
31. ## 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
32. ## 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
33. ## math

3% gets compounded 20 times. 5000*(1.03)^20 = \$9030.56

posted on May 31, 2013
34. ## SCI/220 HUMAN NUTRITION

What questions?

posted on May 31, 2013
35. ## physics

What kind of length unit is "hm"?

posted on May 31, 2013
36. ## physics

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

posted on May 31, 2013
37. ## 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
38. ## physics

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

posted on May 31, 2013
39. ## 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.

posted on May 31, 2013
40. ## 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.

posted on May 31, 2013
41. ## Physics

what are the choices?

posted on May 31, 2013
42. ## 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
43. ## physics

(average velocity)*(time) = 23.9 m/s*12 s = 286.8 m

posted on May 30, 2013
44. ## 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

posted on May 30, 2013
45. ## 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
46. ## 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
47. ## 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
48. ## 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.

posted on May 29, 2013
49. ## 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
50. ## language (sentence fluency)

D. is most fluent

posted on May 29, 2013
51. ## 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
52. ## 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] =

posted on May 29, 2013
53. ## 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
54. ## physics

Speed is constant and direction is not changing. Therefore acceleration is zero.

posted on May 29, 2013
55. ## 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
56. ## 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
57. ## 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
58. ## 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)

posted on May 28, 2013
59. ## 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
60. ## 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
61. ## 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

X - 15 - 8 -[(X-15-8)/2) = 46 (X-23)/2) = 46 X -23 = 92 X = 115

posted on May 28, 2013
63. ## 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
64. ## 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
65. ## 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
66. ## 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
67. ## math

Your numbers require dimensions. Inches? Centimeters? Meters?

posted on May 27, 2013
68. ## 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
69. ## 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
70. ## 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
71. ## algebra

If "diffance" means difference, the answer is 20. You don't need to use algebra.

posted on May 25, 2013
72. ## 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
73. ## 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
74. ## 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
75. ## 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
76. ## 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
77. ## 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
78. ## 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