Saturday

May 23, 2015

May 23, 2015

Total # Posts: 21,027

**math/compound**

40 periods at a rate of .0615/4 2500 (1.015375)^40=2500(1.841) = $4602.55
*January 3, 2015*

**physics**

since you did not specify the direction very well (41 deg from horizontal or vertical? up or down from horizontal? Up or down from vertical?) I will have to be very general in the answer. Vi = 9.66 sin or cos or -sin or -cos of 41 v = Vi - g t at top v = 0 0 = Vi -9.81 t so t...
*January 3, 2015*

**Algebra2**

g = -32 ft/s^2 in the feet (old American - English) system so (1/2)g = -16 Watch out, most of us use metric units g = -9.81 m/s^2 in which case h = Hi + Vi t - 4.9 t^2
*January 3, 2015*

**Math**

y = -3x - 4n slope = m = -3 y axis intercept, b, is y when x = 0 which is -4n
*January 1, 2015*

**Physics**

If the block moves .40 meters then the line is pulled 5 * .4 = 2 meters (a) the work done by the puller person on that line is W in = 60 N * 2 meters = 120 Joules (b) the useful work done on the block was to lift it .40 meters work out = m g h = 25 * 9.81 * .4 = 98.1 Joules so...
*January 1, 2015*

**Physics**

The basic form of Newton's second law is Force = rate of change of momentum = change of (m V) /time if m is constant this is the familiar form F = m dV/dt = m A but here it is simple to use the more fundamental form change of momentum/time = m v/t = 1 *5/5 Newtons as ...
*January 1, 2015*

**science**

strain proportional to stress
*January 1, 2015*

**science**

I am not sure where the fulcrum is but if it is in the middle then: 20 * 5 = 30 * x x = 5(2/3) = 10/3 from center which is 10/3 + 5 from the boy which is 25/3 = 8 1/3 meters from the boy
*January 1, 2015*

**physics**

R1 = 13/3 = 4.33 m R10 = 2 m T = 5 seconds / 10 waves = .5 s f = 1/T = 2 Hz wavelength = (4.33-2)/9 = .259 meter v = .259/.5 = .518 m/s
*January 1, 2015*

**physics**

Only one where the ball fires a rocket after hitting the floor :)
*January 1, 2015*

**Calculus**

You are welcome.
*December 31, 2014*

**Calculus**

f" = [(-1)(x+1)^3 - 3(1-x)(x+1)^2]/(x+1)^6 = [-(x+1)+3(x-1)]/(x+1)^4 ( I don't understand how you got this!!) Looks like division of top and bottom by (x+1)^2 and also -(1-x) = + (x-1)
*December 31, 2014*

**Algebra**

You are welcome :)
*December 31, 2014*

**Algebra**

These problems are pretty advanced for class that has not reached logarithms.
*December 31, 2014*

**Algebra**

hmmm well, you need 2^something = 1000 2^3 = 8 2^4 = 16 2^5 = 32 2^6 = 64 2^7 = 128 2^8 = 256 2^9 = 512 2^10 = about 1000 so d = about 10 so 2*10 = 20 days. It said approximate :)
*December 31, 2014*

**Algebra**

take the log to any base of both sides for example base 10 log 1000 = d log 2 d = 3/.301 = 9.96 2 day periods or 20 days check my reply to your earlier efficiency problem
*December 31, 2014*

**Algebra-Check my answer please!**

5.9 * 10^12 miles/year *2.2 * 10^6 years = 12.98 * 10^18 = 1.298 * 10^19 I get
*December 31, 2014*

**Algebra**

up to the left, and up to the right d^2 = (2-a)^2 + (1-7)^2 d^2 = 45 = 4 - 4 a + a^2 + 36 5 = a^2 - 4 a a^2 - 4 a - 5 = 0 (a-5)(a+1) = 0 a = 5 or a = -1
*December 31, 2014*

**Physics**

You are welcome.
*December 31, 2014*

**Physics**

LOL, yes, depends on purity of water etc. Those numbers are the same to me :)
*December 31, 2014*

**Physics**

water is 4186 Joules/kg deg C 110,000 kg 8 deg C so heat out into water = 4186*110,000*8 = 3.68 * 10^9 Joules into water electricity in = 150,000 * 28 * 3600 = 1.51*10^10 Joules efficiency = out/in = .368/1.51 = .244 = 24.4 %
*December 31, 2014*

**Physics**

If you understand 2, I think you can do 3 You need to look up heat capacity of water in Joules/kg deg C
*December 31, 2014*

**Physics**

2. 1 watt hr = 3600 watt seconds or Joules so 2.0 Mwh = 7200 MJ 33 MJ/kg * m in kg *.18 = 7200 MJ m = 1212 kg
*December 31, 2014*

**Physics**

electrical work in = 180,000 *120 = 21.6 *10^6 Joules mechanical work out = 10,500*9.81*218 = 22.5 *10^6 Joules magic? on moon? let's see ? 10th floor about 9 * 3 meters high or 27 meters, not 218 meters
*December 31, 2014*

**Graphing**

(2+3)/(-5-3) = (y+3) / (x-3) 5/-8 = (y+3) / (x-3) 5 x -15 = -8 y -24 5 x + 8 y = -9 5+8-9 = 4
*December 31, 2014*

**Chemistry missing data**

same amount of what ?
*December 31, 2014*

**Algebra**

(-3-7)/(5+2) = (a-7)/(3+2) -10/7 = (a-7)/5 etc
*December 31, 2014*

**Algebra**

second function, the one in the table, when x goes up 2, y goes up 4 always so y = (4/2) x + b = 2x+b when x = 1, y = 5 so 5 = 2(1) + b b = 3 so y = 2 x + 3 both of your functions are straight lines that go through (0,3) the original one has slope = 4 the second one has half ...
*December 31, 2014*

**calculus**

Good luck :)
*December 31, 2014*

**calculus**

Approximate ³√26 by using an appropriate linearization. y = x^(1/3) we know that if x = 27, y = 3 so I will start there. Of course you could do something else. dy/dx = (1/3) x^-2/3 at x = 27 dy/dx = (1/3) /9 = 1/27 = m so y = (1/27) x + b 3 = (1/27)(27) + b b = 2 so...
*December 31, 2014*

**calculus**

b should come out just like a :)
*December 31, 2014*

**calculus**

y = m x + b at (25,5) 5 = m (25) + b what is m, the slope, there? y = x^.5 dy/dx = .5 x^-.5 = .5/5 = .1 = m so 5 = .1 (25) + b 2.5 = b so our line through (25,5) is y = .1 x + 2.5 now if x = 26 y = 2.6 + 2.5 = 5.1 that is part a check it sqrt 26 = 5.099 Awful close !!! :)
*December 31, 2014*

**physics**

v = 10 t = 30 m/s = 3000 cm/s
*December 30, 2014*

**physics**

F = C coef v^2 (some area) if there is flow separation probably the cross sectional area is the important one pi r^2 if there is little flow separation then maybe surface areas 4 pi r^2. coefficients for spheres are shown both ways they may want you to say F = (6 pi)coef of ...
*December 30, 2014*

**math**

-20 x - 5 = 15 -20 x = 20 x = -1
*December 30, 2014*

**maths**

I am not sure there is much you can do but calculate the values.
*December 30, 2014*

**Algebra 2**

they are equal to 15 when m = 5 Plan A is more expensive if m>5 Plan B is more expensive for m <5 so you want m>/= 5, C
*December 29, 2014*

**Physics**

2 and 4 are correct as are others using 0.15 for initial velocity up. However I am quite sure that was not the intent because the velocity is so low it makes little sense and the shot hardly gets above the hand.
*December 29, 2014*

**Physics typo ?**

you seem to have both 15 and .15 for the velocity. Compromise at 1.5 maybe?
*December 29, 2014*

**Physics**

Let's assume the acceleration, a , is constant then the force is constant F = m a work = integral of force dx from low speed to high speed which is force * (Xend - Xbegin) because F is constant so we need to know x begin and x end let x begin be 0 then d^2x/dt^2 = a dx/dt...
*December 29, 2014*

**PRE-CALC**

2,000 e^.06 t 2,000 e^.24 2,000 * 1.27124915 $ 2,542.50
*December 29, 2014*

**Algebra 1**

3/4 = (y-6)/(x+4) take it from there
*December 29, 2014*

**Precalculus**

agree with Reiny. Note the problem here is really not the algebra but the problem of keeping significant figures when subtracting numbers that are close to each other. However, you must start by doing the algebra correctly :)
*December 29, 2014*

**Precalculus**

NOTE - Steve left a tan 33 out of 800 tan 33 http://www.jiskha.com/display.cgi?id=1419896043
*December 29, 2014*

**Precalculus**

x tan 33 = x tan 35 - 800 tan 33 I do not know how you got what you got, but I just did this problem a few minutes ago and will go find it I hope.
*December 29, 2014*

**sds chemisry**

endo --- put heat in (cure fiberglass resin with a heat lamp :) exo -- heat comes out (burn wood)
*December 29, 2014*

**Algebra 1**

In other words a V with 45 degree slopes and point at (0,1)
*December 29, 2014*

**Pre-Calculus**

LOL - I bet they were supposed to do it with a slide rule. Otherwise too easy.
*December 29, 2014*

**Pre-Calculus**

800 tan 33 = x(tan 35-tan 33) The problem here is not doing the algebra which is easy, but keeping the accuracy which is hard. When you subtract numbers that are close to each other, you lose significant figures in your calculation. What we need to do is find an accurate way ...
*December 29, 2014*

**science**

Hmmm - a great many of my fellow science students who went on to innovate in technical fields immigrated to the US as students or adults. Look around you if you happen by MIT :) At present I have been helping my grand children with common core math (specifically a Singapore ...
*December 29, 2014*

**science**

Take a stab at answering and someone is likely to help. Surely having much of the adult population questioning the scientific method does not help their children learn what it is about. The problem is much wider than just evolution ( think - climate change) but surely mistrust...
*December 29, 2014*

**Algebra 1**

well we agree but I am wondering - If I buy one can do they give me 30 cents and the can?
*December 29, 2014*

**Algebra 1**

huh? If it were just .50 per can total cost = .50 n but we get .80 off the total cost so cost of the deal = .50 n - .8
*December 29, 2014*

**american history**

Wait a minute - I was thinking Plymouth. John Winthrop was one of the MA Bay colony governors when they moved from Gloucester to Boston.
*December 29, 2014*

**american history**

yes, but I do not remember an s on the end of his name.
*December 29, 2014*

**Math**

y </= -2x + 8 a. -4 </= 8 true b. -1 </=-12 nope c. 0 </= -14 nope d. 1 </= -10 nope
*December 29, 2014*

**I guess this is physics related?**

There are ways to do it accurately in physics labs on the subject, but it requires something better than fast eyes and a stopwatch as a rule :) Taking a movie can work if you know the frame rate. However usually you have a paper tape or something being marked every fraction of...
*December 29, 2014*

**I guess this is physics related?**

According to Galileo, if there were no air friction objects of different masses would all fall at the same acceleration, g if straight down and g cos theta if at an angle. Therefore I suspect that mass is simply not important here and an error in measuring it, or in fact ...
*December 29, 2014*

**So what about this one bob? Physics**

That is correct.
*December 29, 2014*

**Algebra 1**

You are welcome.
*December 29, 2014*

**Algebra 1**

7 [ 63/(25 - 4) - 1 ] ??? 7 [ 63/21 - 1 ] 7 [ 3-1] 7 [ 2 ] 14
*December 29, 2014*

**Math**

note e^0 = 1 g' = a e^ax + f' g'(0) = a + 5 g" = a^2 e^ax + f" g"(0) = a^2 + 7 =============================== note cos(0) = 1 and sin(0) = 0 h = cos kx [f] + sin x h' = cos kx f'(x) - f(x) sin kx + cos kx h'(0) = 5 - 0 + 1 = 6 so the ...
*December 29, 2014*

**Math**

v = s^3 dv = 3 s^2 ds at s = 50 v = 125,000 dv = 3 (2500) ds = 7500(.1) = 750 100 (750/125,000) = .6 %
*December 29, 2014*

**Calculus- Can you help me solve for dr/dt**

You are welcome. Actually I am retired now :)
*December 29, 2014*

**Calculus- Can you help me solve for dr/dt**

The change of volume of a sphere with increasing radius is the surface area of the sphere times dr. Draw a picture ! In other words: dV = 4 pi r^2 dr so dV/dt = 4 pi r^2 dr/dt so here 15 = 4 pi r^2 dr/dt or dr/dt = 15 /(4 pi r^2) ---------------------- note , I am a ship ...
*December 29, 2014*

**geomentry**

Its volume is 27 times the old volume (3*3*3)
*December 28, 2014*

**Physics**

You are welcome. Remember potential is always a difference (In height, voltage, whatever).
*December 27, 2014*

**Physics**

10,000 meters the horizontal distance is irrelevant.
*December 27, 2014*

**^Maths^**

good point :)
*December 27, 2014*

**^Maths^ typo**

301 base 6 1*10^0 + 0*6^1 + 3*6^2 should be 301 base 6 1*6^0 + 0*6^1 + 3*6^2 = 109
*December 27, 2014*

**^Maths^**

By the way, I just did that by common sense. I do not know what routine you are really supposed to know. You may have a better way to shift back and forth.
*December 27, 2014*

**^Maths^**

451 base 6 1*6^0 + 5*6^1 + 4*6^2 = 1 + 30 + 144 = 175 in base 10 301 base 6 1*10^0 + 0*6^1 + 3*6^2 = 1 + 0 + 108 = 109 in base 10 so in base 10 175 - x = 109 x = 66 in base 10 put that in base 7 7^2 = 49 17 left 2*7^1 = 14 3 left so 1^7^2 + 2*7^1 + 3*7^0 or P = 123 in base 7
*December 27, 2014*

**physics**

Note equation 1.78 seems to be missing an = sign just left of the integral sign
*December 27, 2014*

**physics**

try deleting the s on https http://books.google.com/books?id=PTj2eEbT_jQC&pg=PA67&dq=elongation+of+long+hanging+rod+due+to+own+weight&hl=en&sa=X&ei=7TGfVI_7NcufgwSx-YKYCg&ved=0CGwQ6AEwCQ#v=onepage&q=elongation%20of%20long%20hanging%20rod%20due%20to%20own%20weight&f=false
*December 27, 2014*

**physics**

Looks like a MIT 8:01 problem to me :) It is too much for me at present but this link might help a little: https://books.google.com/books?id=PTj2eEbT_jQC&pg=PA67&dq=elongation+of+long+hanging+rod+due+to+own+weight&hl=en&sa=X&ei=7TGfVI_7NcufgwSx-YKYCg&ved=0CGwQ6AEwCQ#v=onepage&...
*December 27, 2014*

**Physics**

2.3/2 = 1.15 seconds to go up 0 = Vi -4.9 t = Vi - 4.9*1.15 Vi = 5.365 m/s initial speed up the second ball must have same initial vertical component of velocity = 5.365 m/s Vi sin 60 = 5.365 so Vi = 6.51 m/s
*December 27, 2014*

**PHYSICS**

initial momentum west = 1720 v -1510(75.7) = final momentum west = (1720+1510)15.5
*December 27, 2014*

**math**

LOL ali 3/8 * 80 = 30 5/8 * 80 = 50 30/50 = 3 / 5
*December 26, 2014*

**math**

3 + 5 = 8 so 30new + 50top
*December 26, 2014*

**math**

If a student keeps asking similar questions the student needs to look at earlier replies and try to do the next one without help Jack. We can then check the answer but just telling the student how to do it time after time helps not in the least.
*December 26, 2014*

**math**

yes, ok 24/9 = 8/3 same answer
*December 26, 2014*

**math**

24/36 = 2/3 (2/3)4 = 8/3 or 2 2/3
*December 26, 2014*

**math**

(1/4)(25)sqrt 3 = 10.8 cm^2
*December 26, 2014*

**physics**

How about different colors :) ?
*December 26, 2014*

**math**

pi r^2 = s^2 4 s + 2 pi r = 3600 it seems they want you to use x for 2 pi r so r = x/(2pi) pi r^2 = x^2/(4 pi) = s^2 so 4 s + x = 360 2x/( sqrt pi) + x = 360 2.13 x = 360 x = 169.1 cm 360 - x = 4s = 190.9 cm s = 47.7 ------------------------- check r = x/(2 pi) = 26.9 pi r^2...
*December 26, 2014*

**6th grade math**

1 serving = 0.8 cups 4 cups (1 serving/.8 cups) = 5 servings or 4 * 1/ (4/5) = 20/4 = 5
*December 26, 2014*

**science typo ?**

do you mean 220 volts ? i V = 2,000 220 i = 2000 i = 2000/220
*December 26, 2014*

**maths**

if sin A = 1/2 then cos A = (sqrt 3)/2 because that is a 30, 60, 90 triangle (1/8) 3 * 3^1/2- (3/2) * 3^1/2 = -(9/8) * 3^1/2
*December 26, 2014*

**physics**

1 kg * g = (3+4) a a = g/5
*December 25, 2014*

**binomial**

if only allowed up to x^3 do it in two steps result for (x+8y)^3 * (x+8y)^2 that is easier anyway
*December 25, 2014*

**Math**

Just graph a few points working both ways from ( 0 , -2 )
*December 24, 2014*

**Math**

when x = 0, y = -2 Y increases at 45 degrees from there in both directions so it is a V with the bottom point at (0 , -2)
*December 24, 2014*

**Algebra 2**

well, we know that sqrt 4 = 2 so the answer is (1/2) sqrt 3 however in general to clear the denominator: multiply top and bottom by sqrt 4 3 sqrt 3 sqrt 4 / (3*4) = 6 sqrt 3 /12 = (1/2) sqrt 3
*December 24, 2014*

**Physics**

The 90 kg student was standing still, momentum of zero. there was a push for .0003 seconds then his speed was 5 m/s so change in momentum = 90*5 - 90*0 = 90*5
*December 24, 2014*

**Physics**

force = change in momentum / change in time 90*5/.0003 in Newtons by the way .0003 is a very short pushing time, impractical I think. (typo?)
*December 24, 2014*

**CULCULS**

exactly. I am a Naval Architect. We have a hydrostatic characteristic called "tons per inch" which is how many tons of cargo you can add to increase the draft by one inch as a function of draft. It is basically the water plane area * density of seawater :)
*December 24, 2014*

**CULCULS**

v = (1/3) pi r^2 h but r = h/2 so dr = (1/2) dh v = (1/3) pi * 2 r^3 dv/dt = (2) pi r^2 dr/dt dv/dt = pi r^2 dh/dt Note: this is just the surface area * dh/dt
*December 24, 2014*

**Math**

12/4 = 3 4,000 * 1.03^48
*December 24, 2014*

**Algebra 1 - HEY!!!**

HEY, someone named Henry already showed you how to do this sort of problem. Now start doing them yourself. Post your answers.
*December 23, 2014*

**Algebra 1**

none those two lines have the same slope of 5 so they are parallel but they do not have the same y axis intercept so they never touch each other in two dimensional space.
*December 23, 2014*