Saturday

May 28, 2016
Total # Posts: 26,283

**physics**

Coulomb's law: F = k q1 q2/r^2 E = force on unit charge E = F/1 = k q /r^2 = 9*10^9 * 8*10^-6 /4 1.8 *10^4 Newtons/Coulomb like charges repel so in direction away from positive charge
*December 31, 2015*

**science and technology**

assuming that the force is in the direction of the motion then: 80 * 24 = 1920 Joules
*December 31, 2015*

**physics**

(1/2) m v^2 = (1/2)(250) * 25 because 5^2 = 25 = 3125 Joules
*December 31, 2015*

**physics kinematics**

x is downstream y is across x velocity = -2 y velocity = 4 tan T = -2/4 T = 26.6 degrees from straight across or 90-26.6 = 63.4 from straight upstream magnitude = sqrt(4+16) = 2 sqrt 5 = 4.5
*December 31, 2015*

**Math**

(m b + n g) /(b+g)
*December 30, 2015*

**Math**

280(n+1) = 288 (n) 280 = 8 n n = 35 288 * 35 = 10080 seconds or 2.8 hours
*December 30, 2015*

**math**

LOL - only use positive root if above ground.
*December 30, 2015*

**math**

which is -r +/- sqrt(r^2+d^2)
*December 30, 2015*

**math**

d^2 = h^2 + 2 r h h^2 + 2 r h - d^2 = 0 quadratic h = [ -2r +/- 2 sqrt(r^2+d^2) ]/2
*December 30, 2015*

**Physics**

change in potential energy due to fall = m g (10+x) storage of potential energy in spring = (1/2) k x^2 so (1/2) k x^2 = m g (10 + x) you have everything, solve quadratic for x then: distance below bridge = 10 + x
*December 30, 2015*

**100 kg bullet?**

I assume a typo and bullet is 10 grams initial momentum of bullet and mass before collision = 500 * 10^-2 kg + 0 * 2 kg = 5 kg m/s the momentum just after collision will be the same with a mass now of 2.010 kg and speed v so 2.010 v = 5 calculate v from that now the pendulum ...
*December 30, 2015*

**math**

i and i+5 3(i+5) = 11 + i^2 3 i + 15 = 11 + i^2 i^2 - 3 i - 4 = 0 (i-4)(i+1) = 0 i = 4 or i = -1 try 4 then i+5 = 9 is 9 five more than 4, yes is 27 = 11 + 16 yes so 4 and 9 work try -1 i+5 = 4 is 12 = 11 + (-1)^2 yes so -1 and 4 work
*December 30, 2015*

**Algebra I**

-6(3x+1) ----------- 2 (3x+1) = -3
*December 30, 2015*

**math**

try 4 (5 + 6 g)
*December 30, 2015*

**Precalculus- HELP!**

hmmm think it means t = 33 + 7 sin [ (pi/12)(x-11) ] when x = 0 we have sin [-11 pi/12] which is - sin [11*180/12] = -sin(165 degrees) = -.259 so t = 33 - 7(.259) = 31.2 degrees F
*December 30, 2015*

**science,physics**

If you found this question in a physics book, watch the wording. If they asked for "distance", then Ms Sue told you how to do it. If they ask for "displacement", that is the magnitude of the vector between the start and the finish which is zero.
*December 30, 2015*

**Math**

1.3 * 6 * 160
*December 30, 2015*

**math**

lost 5 won 15 played 20
*December 30, 2015*

**Math**

k = m +7 3(m+7) + 5 m = 165
*December 30, 2015*

**SOCIAL STUDIES**

I thought it an extremely interesting article but wished it contained more details of garden construction. It was also somewhat disjointed and repetitive.
*December 29, 2015*

**Math**

The center has to be on the line y = x if the circle is tangent to the x and y axes. so center on 3 x = 3 y = 9 or (3,3) and the radius is 3 so (x-3)^2 + (y-3)^2 = 9
*December 29, 2015*

**linear programming**

p = number of printmasters s = number of speedmasters (1) vol = 10 p + 5 s < 2000 (2) wt = 5000 p + 600 s < 300000 maximize gain = g = 125000 p + 30000 s p on x axis , s on y axis do quadrant one vol line (0,400) to (200,0) wt line (0,500) to (60,0) find intersection ...
*December 29, 2015*

**Chemistry**

CuSO4 is 159.6 grams/ mol 5 M would be 159.6*5 = 798 grams/1000 mL so we need 79.8 grams to make 100 mL of 5M take one tenth of that solution, 10 mL and mix it with 90 mL of water to make 100mL of .5 M take one fifth of that .5 M solution which is 20 mL and mix with 80 mL of ...
*December 29, 2015*

**Math**

p + n = 90 but we know that p is 2 n so 2n + n = 90 or 3 n = 90
*December 29, 2015*

**Math**

p + n = 90 p = 2 n 3 n = 90 n = 30 p = 60
*December 29, 2015*

**math**

You are welcome.
*December 29, 2015*

**math**

(3/4) x = 3 1/2 3 x / 4 = 7/2 3 x = 14 x = 14/3 = 4 2/3
*December 29, 2015*

**math**

8 1/2 / 2 5/6 17/2 / 17/6 1/2 / 1/6 3
*December 29, 2015*

**math**

25 in urn 1 25 in urn 2 2 white - 3/25 * 10/25 2 red - 7/25 * 6/25 2 black - 15/25 * 9/25 add the results
*December 29, 2015*

**maths physics chemistry**

conservation of mass conservation of energy
*December 29, 2015*

**basic mathematics**

for the first draw 20 balls in the box for the second there are 19 the rest is obvious. For example both white ball one: 10/20 =1/2 ball two: 9/19 so (1/2)(9/19) = 9/38
*December 29, 2015*

**Algebra 1 Solving Systems Using Elimination**

I got (-2,6)
*December 28, 2015*

**math**

she drove home 390+70 You need to know the 70 the 164 was part of her vacation there.
*December 28, 2015*

**Physics**

fall 3300 m range = 9400 m speed = s u = constant horizontal speed = s cos 35 = .819 s if t is time in air then t = 9400 / .819 s = 11,474/s Vi = initial vertical speed = s sin 35 = .574 s z = altitude z = 3300 + Vi t - 4.9 t^2 ground is z = 0 so if t is the time in the air ...
*December 28, 2015*

**history**

Whoever your teacher is sure chooses some amusing alternative answers to questions !
*December 28, 2015*

**chemistry, physics please help**

That looks right to me although I call it latent heat of fusion.
*December 28, 2015*

**algebra**

Those are two parallel lines with different y intercepts. They never intersect and there is no solution. 2 x + y = -4 and 2 x + y = 3 each has slope = -2
*December 28, 2015*

**history**

It was NOT Aaron Burr It was not an Island It was not a West Indies rebel Therefore we are left with Napoleon. However I already told you that ! See above: "..... President Jefferson bought it all from Napoleon, whose soldiers were getting sick in the West Indies. ...."
*December 28, 2015*

**history**

Water runs downhill.
*December 28, 2015*

**history**

By the way, Mount Washington is 6289 feet high. It is in New Hampshire. However the Rockies are higher in general than the East Coast mountains.
*December 28, 2015*

**history**

Now no way am I going to do that for you. New Orleans is on your map. Google Louisiana purchase. Also Google Louis and Clark. You are supposed to know about their trip west, much more than I could write here. Yes, the Great Plains are pretty flat and the Rockies are seriously ...
*December 28, 2015*

**history**

LOL - The river is not higher than either the Appalachians or the Rockies. The Rockies are seriously high, even higher than Mount Washington, although they do not collect quite as bad weather.
*December 28, 2015*

**history**

Google: Louisiana purchase President Jefferson bought it all from Napoleon, whose soldiers were getting sick in the West Indies.
*December 28, 2015*

**no graphic**

If you tried to copy and paste, that does not work here.
*December 28, 2015*

**Physics**

r = 1.5 * 10^11 meters 2 pi r = 9.42 * 10^11 meters circumference and 365d * 24h/d * 3600 s/h =3.15 * 10^7 seconds v = 9.42*10^11 m/3.15*10^7 s = 2.99*10^4 m/s Ac = v^2/r etc
*December 28, 2015*

**I do not believe you**

Just too weird. I bet you intended to type: y-3=(8/3)(x+2);(-2,3) That line passes through (-2,3) already, just the slope is wrong. try: y-3=(-3/8)(x+2);(-2,3)
*December 28, 2015*

**physics**

Suspect so :)
*December 28, 2015*

**physics**

Well, at a corner it is infinite since we have that division by zero problem when r = 0 at the middle, find the potential of one of them at a distance of (a/2)sqrt 2 The neat thing about potentials is that they add like scalars. Just multiply by 4.
*December 28, 2015*

**where?**

potential energy is a function of distance from the charges. Where do you want it?
*December 28, 2015*

**trigonometry**

right triangle 3, 4 ,5 each times three base 4, altitude 3 (1/2)4* 4 = 6 m^2
*December 28, 2015*

**parentheses ?????**

What is the numerator and what is the denominator? If something is squared write x^2 cubed write x^3 (2x^4 + 7) maybe ????
*December 28, 2015*

**Math**

6/100 = 3/50 175/1000 = 35/200 = 7/40
*December 28, 2015*

**math**

.3 /(1/7) = 2.1 per mile 2.1 * 26
*December 28, 2015*

**Algebra 1**

(y-2) / (x-5) = 3 y-2 = 3(x-5) the last one
*December 28, 2015*

**typo ? Linear programming problem**

What does this constraint mean? limited by the formula x+2y,+1,400. I have to leave, hope Steve sees this.
*December 27, 2015*

**More typos**

Seems to be a bad typing day hs moment of intial 30kg Suspect you mean moment of inertia but the units are wrong. If it is I = 30 kg m^2 then torque = I alpha alpha = angular acceleration = 40 * 0.20 N m / 30 kg m^2 omega = alpha * t theta = (1/2) alpha t^2 number of revs = ...
*December 27, 2015*

**science**

depends how smooth and how high you push If it is perfectly smooth so the sphere spins freely without any friction force causing it to roll along the table, then that force F is the only net horizontal force on the sphere and a = F/m
*December 27, 2015*

**Math**

2(sinx/(1+cosx))d/dx (sinx/(1+cosx)) let y = sinx/(1+cosx) dy/dx=[(1+cos)cos + sin cos ]/(1+cos)^2 = cos[ 1+cos + sin]/ (1+cos)^2 so put that back in 2(sin/(1+cos))*cos[1+cos+sin]/ (1+cos)^2 2 sin cos(1+cos+sin)/(1+cos)^3 I do not see any simplification either.
*December 27, 2015*

**math**

f' = 2 x /(x^2+1) f" = [ 2(x^2+1)- 2x(2x) ]/(x^2+1)^2 = [ 2x^2+2 -4 x^2 ]/(x^2+1)^2 2[1-x^2] /(x^2+1)^2
*December 27, 2015*

**whoops trick question**

Vi = 17 sin 20 = 5.81 t = 5.81/9.81 =.593 seconds upward so in the air 2*.593 = 1.19 seconds in the air so it is not in the air for five seconds and the answer to part a is d = u t = 17 * cos 20 * 1.19 = 19 meters
*December 26, 2015*

**physics**

I guess you mean 20 degrees above horizontal. u = horizontal velocity, does not change = 17 cos 20 so a) (17 cos 20)4 b) u = 17 cos 20 At the highest point, there is no vertical velocity, so the answer is u = 17 cos 20
*December 26, 2015*

**Precalc**

The i and j are unit vectors in the x any y directions. This vector is of magnitude 2.83 and its direction is 45 degrees counterclockwise from the x axis so its components are X direction: 2.83 * cos 45 Y direction: 2/83 * sin 45 so: i * (2.83*cos45) + j*(2.83*sin45)
*December 26, 2015*

**Mathematics**

draw altitude from center of circle to center of chord. length 12 half of chord length 5 5, 12, 13 right triangle results r = 13
*December 26, 2015*

**dr.khastagir govt girls high school**

let c = tan A d = sin A P = c + d so p^2 = c^2 + 2 c d + d^2 q = c - d so q^2 = c^2 - 2 c d + d^2 p^2+q^2 = 2 (c^2 + d^2) = 2 (tan^2 A + sin^2 A) so what is the question?
*December 26, 2015*

**basic allied math**

deci
*December 25, 2015*

**English**

1. is ok 2. is not A study is a discrete thing. If there were several studies you would say "according to studies". However you would not say "a research" because research is an action. It should be; "According to research"... or according to ...
*December 24, 2015*

**Chemistry**

I think you will get Zinc Oxide which you put on your nose to prevent sunburn. White gooey stuff. At the same time you will increase the temperature of earth by releasing carbon dioxide into the atmosphere. This has little effect on the incoming ultraviolet that burns your ...
*December 24, 2015*

**Stats**

http://davidmlane.com/hyperstat/z_table.html
*December 24, 2015*

**Physics**

You are welcome. Check my algebra of course.
*December 23, 2015*

**Physics**

http://www.jiskha.com/display.cgi?id=1450909117
*December 23, 2015*

**Physics**

That sure looks familiar
*December 23, 2015*

**physics 1**

height of cliff = h height of top of second experiment = h + 2 Experiment 1: h = (1/2) g t^2 = (1/2) g (4.15)^2 h = g (8.61 ) so g = h/8.61 Experiment 2 rise part: initial speed up = Vi v = Vi - g t v = 0 in 2 meter rise 0 = Vi - g trise so trise = Vi/g 2 = Vi trise - (1/2) g...
*December 23, 2015*

**Math**

well what are the choices for tens digit 1 ---> 3 2 ---> 6 3 ---> 9 and bigger will not work so 13 26 39
*December 23, 2015*

**physics**

cyclist 1 1 hour out 20/15 = 4/3 hour back total time = 7/3 hour so the second wants to go out for (1/2)(7/3) hours = 7/6 hour at 10 km/hr 70/6 = 11 2/3 kilometer
*December 23, 2015*

**algebra**

multiply first equation by 5 and the second equation by 3 20 x + 15 y = 60 21 x + 15 y = 78 ------------------subtract -1 x = - 18 so x = 18 now go back and find y
*December 23, 2015*

**Physics**

http://www.jiskha.com/display.cgi?id=1450906690
*December 23, 2015*

**History**

Hey, they have to blame it on the natives and make themselves feel justified.
*December 23, 2015*

**Mathematics**

well try 11 of course you could do 14/ 8 which gives 22 or 28/16 etc etc but they asked for the LEAST
*December 23, 2015*

**Math**

- 1/sin^2 --------------- (1 + cos/sin)^2 -1 ------------------------------ sin^2 [ (1+cos/sin)(1+cos/sin)] -1 -------------------------- (sin+cos)(sin+cos)
*December 23, 2015*

**no copy and paste**

You probably tried to paste the figure but that does not work here.
*December 23, 2015*

**science help**

The one with the lowest frequency has the lowest energy per photon. That means C here I suppose although I have no idea what D is. A fish?
*December 22, 2015*

**science help PLS**

Transverse is like a guitar string Longitudinal is what we are talking about with sound. Both types propagate.
*December 22, 2015*

**whoops**

Oh sorry, missed the - sign -14 +16 = 4 D
*December 22, 2015*

**Algebra**

huh? 14 + 8 * 2 = 14+16 = 30
*December 22, 2015*

**English**

I could get to the bus stop where I had to get off. My school is near the bus stop. I narrowly entered the school gate. Many students were running into the school gate not to be late. ============================ Maybe: The bus reached the bus stop near my school where I get ...
*December 22, 2015*

**physics**

first do the sidewalls that is a uniform disk of radius Rout minus a uniform disk of radius Rin (You did not give me the outside radius of tire and inside radius of tire) Then you have the easy part, the thread which is simply m Rout^2 of course to do m you need to do the ...
*December 22, 2015*

**Algebra 2 (Math)**

I agree
*December 22, 2015*

**Dr.tsegay**

a + 2 d = (3/4)[ a + 5d ] and 2 a + 7 d = 60 ------------------------ (1/4 a -7/4 d = 0 or 1 a - 7 d = 0 2 a + 7 d = 60 ------------------- add 3 a = 60 a = 20 d = 20/7 an = 20 + (n-1)(20/7)
*December 22, 2015*

**Chemistry**

half life of carbon 14 is about 5730 years .125 = (1/2)^n where n is the number of half lives log .125 = n log .5 n = 3 half lives 3 * 5730 = 17,190 years old
*December 22, 2015*

**metreology**

This question is so important to us that I am going to answer it just to make sure you know. Radiation comes in from the sun in a wide spectrum but maximum ultraviolet although as you know there is lots of visible. That energy mostly gets used to power things like plants and ...
*December 22, 2015*

**Math**

Not enough information c^2 = a^2 + b^2 P = a + b + c = 40 or P = a + b + sqrt(a^2+b^2) = 40 now if it is isoceles, a = b, then P = 2 a + sqrt (2 a^2) = 3.414 a = 40 A = (1/2) a b = (1/2)a^2 = (1/2)(40/3.414)^2 = 68.6
*December 22, 2015*

**physics**

1. Well, first of all The average VELOCITY is ZERO because it went nowhere. The arrow from the starting point to the end point has no length, no displacement. the average speed however id the total distance 8 km / 22 min 2. 83 km/hr(1 hr/3600 s)(1000 m/km)= 23 m/s v = Vi + a t...
*December 22, 2015*

**math**

10.5 km/cm which is 1,050,000/1
*December 22, 2015*

**math**

385 ( 1 in/25 mi) = 15.4 in
*December 22, 2015*

**Huh?**

How would I know? I have no idea what a or d is.
*December 22, 2015*

**math**

I have no ideas because I do not know the shape or the scale
*December 22, 2015*

**math**

6 ft (9.6/12) = 4.8 ft
*December 22, 2015*

**science**

CaO + 2HNO3 ---> H2O + Ca(NO3)2 ?? CaO = 40 + 16 = 56 grams/mol so we have 1.5/56 = .0268 mols of CaO
*December 22, 2015*

**science help**

You need a good storage system so you can provide energy left over from the windy days on the calm days. (super batteries, pump up to a reservoir, flywheels, whatever.
*December 21, 2015*

**science help**

Yes of course. The others are nutty.
*December 21, 2015*