# Posts by Damon

Total # Posts: 31,634

**Mathmatics**

120/360 = 1/3 so we want one third the area of the circle (1/3) pi (81) =

**Math**

7 (10 + 2 ) ?

**Algebra**

s = height above ground s = 60 + 20 t - 4.9 t^2 (standard physics equation on earth) at t = 0 s = 60 (clearly :) now when does it hit the bleak earth? That is when s = 0 4.9 t^2 - 20 t -60 = 0 solve quadratic and use the positive t (the negative t was back before you threw it ...

**Algebra (answer check)**

hmmm .94^6 * 12500 = 8623 slope = m = (5-2)/(-3+4) = 3 y = 3 x + b 5 = 3(-3) + b 5 = -9 + b b = 14 so y = 3 x + 14 so none of your answers. You probably have a typo. even is 2, 4, 6 so 4 of the six sides are even or 5 4/6 = 2/3

**physics**

to prevent sliding down: F sin T >/= m g - mu m g cos T to prevent sliding up F sin T </= m g + mu m g cos T

**physics**

If theta is the angle above horizontal and there is no friction then F sin theta must be = m g if theta = 0 , F is infinite if theta = 90 degree, F = m g

**math**

Area of what I assume is supposed to be a rectangle is (1/2)(1/4) = 1/8 of a square mile

**Algebra**

In A there are two values of y , -2 and + 2, for the same value of x, 4 That is a no no

**Algebra**

You are welcome.

**Algebra**

I guess maybe you mean: x/(x-2) + (x-1)/(x+1) = -1 multiply everything by (x-2)(x+1) x(x+1) + (x-1)(x-2) =-(x-2)(x+1) x^2 + x +x^2 -3x +2 = -[ x^2-x-2 ] 2 x^2 -2x +2 = -x^2 + x + 2 3 x^2 - 3 x = 0 3 x (x-1) = 0 x = 0 or x = 1

**Math**

well ok, then your way so let (1 - x/100) = z 1/2 = z^8 ln .5 = 8 ln z so ln z = -.693/8 = - .0866 then z = e^-.0866 = .917 x/100 = 1-.917 = .083 so x = 8.3 % note my way uses continuous rate, yours is yearly change.

**Math**

dn/dt = -(x/100) n dn/n = -(x/100) dt ln n = (-x/100 + C n = e^(-x/100 + C)t or n = c e^-(x/100)t at t = 0, n = N so c = N at t = 8, n = N/2 so c = N and N/2 = N e^-8x/100 or .5 = e^-.08x ln .5 = -.08 x -.693 = -.08 x x = 8.725 %

**Dynamics**

Ac = v^2/R mg sin a = mv^2/R so sin a = v^2/(R g) and v = 100,000/ 3,600 = 27.8 m/s solve for angle a

**Dynamics of rigid bodies**

tan 10 = m v^2/R / mg = v^2/(R g) but R/0.40 = sin 10 so R = 0.40 sin 10 T = m sqrt [(v^2/R)^2 + g^2]

**Dynamics of rigid bodies**

when v^2/R = g, that is it

**Dynamics of rigid bodies**

m omega^2 R = 400 0.300 w^2 (0.60) = 400 solve for w ( omega ) in radians/sec then w * 1 rev/2pi rad * 60 sec/min = RPM

**Dynamics of rigid bodies**

impulse = change of momentum force = impulse/time

**Chemistry**

How do you expect to get from mL to moles if you do not know how much HCl is in the water? Where did you get the 1.19 ? That is why we do not understand your answer.

**sir steve damon reiny steve help maths**

Well, it depends where he is I think at the beginning x = man from light pole= Xi then x = Xi + 1.5 t if he starts at the pole at t = 0 then Xi = 0 but we can not assume that y = shadow length=(2/6)(x+y) or y = x/2 so y=(1/2)(Xi + 1.5 t) and dy/dt = (1/2)(1.5) = 3/4 m/s

**Algebra**

do you mean sqrt (97x)???? 97 is a prime number so if we have sqrt(97*97) that is 97 so x = 97 works 97 times any perfect square like 4 or 9 also works

**I did the first one below. **

Now you try.

**algebra 1**

x - 5 remainder 5 ------ x - 5 ==== ________________ x-5 |x^2 - 10 x + 30 ==== x^2 - 5 x =====-------------- ======== - 5 x + 30 =========- 5 x + 25 ---------------------- =======Remainder = 5

**Algebra 2**

at two pi they are both zero but at pi/2 sin is 1 and tan is oo at pi/3 sin is sqrt3/2 and tan is sqrt3 at 3 pi/2 same problem as at pi/2

**Science**

Yes.

**solve what?**

Did you try to copy and paste an equation? That does not work.

**Engineering Systems**

A vehicle jack exerts at least two forces, one up on the vehicle equal to the vehicle weight and one down on the ground equal to the vehicle weight plus the jack weight. Of course gravity exerts a force equal to the vehicle weight so that the net force on the jack is zero. You...

**math science geography**

change in momentum = Force * time = 15*4 = 60 kg m/s

**Math**

assuming that it is 3/4/13 by mass and not by atoms: 3x + 4x + 13 x = 4 kg 20 x = 4 x = .2 kg Ni = 3x = .6 kg Zn = 4x = .8 kg Cu =13x = 2.6 kg

**algebra 1**

well, I need two numbers one apart that multiply to 156 try 12 and 13 :) (y-13)(y+12) for 39 they must differ by 9 3 and 13 nope, both prime so no other way ,,, hopeless too bad it was not r^2-10r -39 :)

**Science**

They tell you that the water has to seep through it. Therefore concrete, packed clay, plastic sheeting, and roof tar, all of which are supposed to be waterproof, will NOT work. Use the sandy gravel.

**Math**

50 t - 40 t = 18

**Math**

d = v t 60 t = 40 (t+1) 20 t = 40 t = 2 so d = 60*2 = 120 miles or d = 40*3 = 120 miles

**Science**

whoops, Dr Bob is right, Ph is neutral ,about 7.

**Science**

nono3 is a base, not acid. It should turn the phenolpthalein pink if the Ph is over about 8

**Math**

LOL, thanks ! Misread it.

**Math**

speed = 50 miles/60 minutes d = v t 5 = (5/6) t t = 6 minutes 4:54 pm

**Geometry**

using law of cosines 8^2 = 7^2+9^2 - 2*7*9 cos A 64 = 49 + 81 - 126 cos A cos A = 66/126 x^2 = 130 - 126 cos(180-A) but cos(180-A) = -cos A so x^2 = 130 + 126(66/126) x^2 = 196 x = 14

**Physics HELP!**

if they stick together: original momentum = 2.1*10^4 * 2 final momentum = 4.2*10^4*v so v = 1 m/s initial ke = (1/2)m v^2 final ke = (1/2)(2m)(v/2)^2 final/initial = [2v^2/4]/v^2 =1/2 so you lose half =============== LOL if perfectly elastic, first one stops, second continues ...

**math**

for example if you know jack bought 20 apples then 20 = (x-30)/3 60 = x-30 x = 90 for Henry check 90/3 - 10 = 20 for Jack

**math**

(x/3)-10 = Jack = (x-30)/3 yes, the right and the left are equal, but you can not solve for x without knowing more.

**Physics**

force down ramp = m g sin 30 = .5 m g normal force = m g cos 30 maximum friction force = mu m g cos 30 slides if: .5 m g > mu m g cos 30 so mu >/= .5/cos 30 = .58

**chemistry**

1/4 liter so four times 5.9 grams in liter = 23.6 grams in a liter Na = Na2CO3 = 106 grams/mol so molarity = 23.6/106 mols/liter

**Geometry**

half triangle base = 6/tan 30 so base = b = 12/tan 30 sin 60 = h/b so h = b sin 60 A=(1/2)bh =(1/2)(12/tan30)(12/tan 30)sin 60

**MMATH08**

15 - 3 = 12 12 * 15 = 180 meters total time = 180 meters/2 meters/sec = 90 sec

**Physic**

x = 2 cos 40 + 4 cos 127 y = 2 sin 40 + 4 sin 127 magnitude^2 = x^2+y^2 tan angle to x axis = y/x

**physics particular paragraph**

The basic functional structure of an optical fiber consists of an outer protective cladding and an inner core through which light pulses travel. The overall diameter of the fiber is about 125 ?m and that of the core is just about 50 ?m. The difference in refractive index of ...

**physics**

better: http://www.boundless.com/physics/textbooks/boundless-physics-textbook/geometric-optics-24/reflection-refraction-and-dispersion-169/total-internal-reflection-and-fiber-optics-609-6258/

**physics**

Snell's Law critical angle http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/fibopt.html

**Math**

by the way 45/41 is bigger than one which is a very improbable probability.

**Math**

p red = 9/41 replace so independent p blue = 10/41 9/41 * 10/41 = 90/1681

**CHEK MATH PLZ!!!**

yes 9/36 = 1/4 yes half of the table :)

**Physics-Answer Check**

1. agree Power = Voltage* current so i = P/V = 4/120 = .0333 amps 2. R = V/i = V*2/P = 3600 ohms 3. Power * time = energy used = 4 * 2 = 8 watt hours = .008 kwhr .008*.12 = .00096 dollars

**Physics**

speed = c = about3*10^8 m/s distance=wave length= speed * time frequency = 1/time E = plank's constant * frequency This is basic. Check your text!!!!

**Physics**

M/m = 1/sqrt(1-v^2/c^2) = 1.15 1 /[1- v^2/(9*10^16)] = 1.15*2

**Dynamics**

both proceed for time t both are at the same position x=d at time t both started at t = 0 at x = 0 for car d = 6 t for cycle d = (1/2) 4 t^2 so 6 t = (1/2) 4 t^2 3 = t then d = 6*3 = 18

**LOL**

Right, you want me to write your text book chapter? Here: http://hyperphysics.phy-astr.gsu.edu/hbase/Bohr.html

**Physics**

v = (2 pi R/4) / 2.1 = pi R/(4.2) Ac = v^2/R F = mAc = m v^2/R

**pls help physics problem**

T = moment at pivot = m g (1.55/2) alpha = T/moment of inertia moment of inertia about end = (1/3)mL^2 = (1/3)(m)(1.55^2) so alpha = g(1.55/2) /[(1/3)(1.55^2)] that is part 1 2) 1.02 alpha 3| g = alpha * x

**Math**

b^2-4ac is positive for real roots 4 - 4(1)(1-m) is positive 4 - 4 + 4 m is positive or 4 m is positive so m is positive m>0 for sure now 2 +/- sqrt (b^2-4ac) is positive for positive root 2 +/- sqrt(4-4(1-m) ) is positive 2 +/- sqrt(m) is positive m < 4 so 0 <m< 4

**Math**

along the x (horizontal) axis you would have time along the y (vertical) axis you would have height so the height is a function of (depends on) time so time is the independent variable and height is dependent on age(time)

**chemistry**

for every mol of N (not N2) you get one mol of NH mols of N = 32 g /14 g/mol = 32/14 so we get (32/14) mols of NH3 NH3 = 14+3 = 17 g/mol so (32/14)(17) grams

**Math**

I guess we are talking about one one year period .08x + .06(4800-x) = 348

**Science**

A chemical reaction?

**Trig Help Please**

200 - 30 = 170 sin 42 = 170/x

**Trig**

same as your smokestack problem sin 35.2 = 16/x

**math**

Now about that power stuff, If we can agree that log(ab) = log (a) + log (b) then what is log (a^3) ???? well log (a*a*a) = log(a)+log(a)+log(a) which is of course 3 log (a) :)

**math**

http://en.wikipedia.org/wiki/Slide_rule

**math**

it arrives at 3:54 which is 3:(54-12) = 3:42 on my watch So I probably missed it by seven minutes.

**physics - sort of**

a) Displacement is the vector from the start point to the finish point. We ended up where we started. So ZERO !!!! (this was a trick question) b) I guess we do not know that g = 9.81 m/s^2 or we would not need that 2 seconds given. v = Vi - g t at top v = 0 Vi = g t = 2 g 12...

**stats**

.8*200 = 160 then http://davidmlane.com/hyperstat/z_table.html

**Physics**

max Pe = max Ke (1/2)k Xmax^2 = (1/2) m Vmax^2 (1/2)(400)(.1)^2 = (1/2)(.3)(Vmax)^2 40/3 = Vmax^2

**Social Studies**

I agree. More money deposited for banks to lend out means lower interest rates.

**Engineering science**

a. displacement = sqrt(600^2+420^2) b. distance = 600+420 = 1020 so speed = 1020/time c.average velocity = answer from part a / time but velocity also has a direction since it is a vector tan angle east of north = 420/600

**Fluid Dynamics**

If there were no frictional losses, no, the velocity would increase to maintain the same flow rate which is velocity times area. However In real life as the velocity increases the losses of total energy due to friction (viscosity) increase and the flow will slow down for a ...

**Math Help?**

x<0 is left y<0 is down so down to the left = Third quadrant :)

**algebra**

The form is y = m x + b m is the slope b is the y axis intercept, where the line hits the y axis when x = 0 so the slope here is m = 2 and the line will look like y = 2 x + b so it is not C and it is not D now what happens when x = 3? y = 2(3) + b = 6+b but y better be 8 so b ...

**Math**

b would be used to eliminate x but you are supposed to eliminate z so c which would give you -4z+4z = 0

**Science please help**

A system which if disturbed tends to return to equilibrium is stable. Think pendulum. A system that if disturbed tends to run away from equilibrium is considered unstable, think pencil standing on your desk on its eraser. Once it falls flat on your desk of course, it becomes ...

**TRIG**

cos 32.1 = side/diagonal = 142.9/x so x = 142.9 / cos 32.1

**Physics**

1 atm = pressure at surface = 101325 Pascals or Newtons/meter^2 p = pressure at surface + density*g * depth so 3 atm at 2 atm below surface = 202650 Pascals = 1240 * 9.81 * depth so depth = 16.7 meters

**Physics**

In the vertical direction mg down from gravity = mg up from the floor so the vertical acceleration = 0 In the horizontal direction there is only one force, friction, deaccerating -0.30 m g = m a so a = -0.30 g = -0.30 * 9.8 =-2.94 m/s^3 Now if the initial speed is 3 then v = 3...

**physics**

use sci units L = 2.50 meters m = 0.5 kg g on earth is about 9.81 m/s^2 amplitude of .25 is irrelevant to usual approximation but see http://en.wikipedia.org/wiki/Pendulum ignoring amplitude: T = period = 2 pi sqrt (L/g) T = 2(3.14)sqrt (2.5/9.81) seconds frequency = 1/T Hz

**math-precalculus**

radius = 25 height of center = 26 T is angle from vertical height = 26 + 25 cos T so 44 = 26 + 25 cos T 25 cos T = 18 cos T = .72 T = 44 degrees from vertical so 88 degrees out of 360 are above 44 meters (88/360)6 = 1.47 minutes

**Science**

A thrown football has both speed and height. The speed results in kinetic energy Ke = (1/2) m v^2 The height gives potential energy Pe = m g h The sum of potential and kinetic is constant if there is no air drag. That is the total mechanical energy. As the height goes up, the ...

**Math**

c = 0.30 * total so total = c/0.30

**Physics 1401**

object mass = 30/g weight of water displaced = (30-20) = 10 N water weight = water mass * g so water mass = 10 N/g but water volume = water mass * 1 m^3/1000 kg so water volume = (10/g)/1000 meters^3 water volume = .01/g = object volume so object mass/object volume = object ...

**algebra**

downstream speed = (v+c) upstream speed = (v-c) time = t (v+c)t = 45 (v-c)t = 27 (12+c)t = 45 (12-c)t = 27 so 45/(12+c) = 27/(12-c) 45 (12-c) = 27 (12+c) etc

**calculus**

I may look easy but it took me a while :)

**calculus**

dy/dx=cos x+ z sec^2 x+ dz/dx tan x = z + cos x so z = z sec^2 x + dz/dx tan x z(1-sec^2x) = dz/dx tan x z (-sin^2x/cos^2x) = dz/dx (sin x/cos x) z(-tan x ) = dz/dx dz/dx = -z tan x ------------------------- d/dx(z+cos x)=d^2y/dx^2=dz/dx-sin x = -z tan x-sin x which lo and ...

**Science please help**

also non-animal things like styrofoam, fiberglass insulaton, vacuum, etc, etc, etc

**trigonometry**

3,4,5 right triangle so sin = 4/5 so cosec = 5/4 tan = 4/3 so cot = 3/4 so (5/4)/(1 + 3/4) = 5/7

**math**

50 = 35 t - 5 t^2 5 t^2 - 35 t + 50 = 0 t^2 - 7 t + 10 = 0 (t-5)(t-2) = 0 2 on the way up and 5 on the way down

**Math**

divide both sides of 5 (3cd+b) = A(3cd+b) by (3cd+b)

**Math**

hummm 6+9 IS NOT 18 BUT 15 6 c d + 2 b + 9 c d + 3 b = A(3cd+b) 15 c d + 5 b = A(3cd+b) 5 (3cd+b) = A(3cd+b) A = 5

**Chemistry**

NH3 = 14 + 3 = 17 grams/mol 203.5/17 = 12 mols of NH3 so 12 mols of HCN result HCN = 1 + 12 + 14 = 27 grams/mol so 12 * 27 grams HCN

**at STP ?**

.27 mols HCl agree so .135 mols CO2--- agree at standard temp and pressure a mol is 22.4 liters .135 mol*22.4 liters/mol= 3 liters a liter is 1000 cm^3 so I get 3,000 cm^3

**math**

well it is more than 180 and less than 270 so I claim it is in the third

**Math**

LOL, you have to be more explicit about what you want. For example: x^2 + y^2 = r^2 is a formula for a circle of radius r and center at the origin in x,y plane

**Calculus**

when y = 1, x = 1 when y = 8, x = 2so we seem to be talking about the sort of triangle between (1,1) (2,1) and (2,8) could be vertical cylinders of wall thickness dx and height (x^3-1) and radius x from x = 1 to x = 2 v = integral [2 pi x(x^3-1)]dx from x = 1 to x = 2 2 pi [ x...

**typo and easier way**

by the way, you could have used the average speed Vav = 3*10^6 so t = 10^-2/3*10^6 = (1/3)*10^-8 (not 10^-10)