Friday

May 29, 2015

May 29, 2015

Total # Posts: 21,075

**5th grade Science**

the density of water is about 1 g/cm^3 This boat is more dense than water, it is in fact more like a rock than most plastic and is certainly not hollow. the upward force on an object in water is the weight of water displaced by the volume of the object in the water. If the ...
*March 8, 2015*

**Social studies**

http://www.u-s-history.com/pages/h127.html
*March 8, 2015*

**geography**

Oh, the s makes it hard http://eos.ucs.uri.edu/EOSWebOPAC/OPAC/Details/Record.aspx?TaskCode=61612&BibCode=EOSMAIN|5127150|1|288252&HitCount=1&SelectionType=1&SearchType=2&CurrentPage=1&IndexCode=-1&SortDirection=Descending
*March 8, 2015*

**geography**

My students worked on one: https://eos.ucs.uri.edu/EOSWebOPAC/OPAC/Details/Record.aspx?TaskCode=61612&BibCode=EOSMAIN|5127150|1|288252&HitCount=1&SelectionType=1&SearchType=2&CurrentPage=1&IndexCode=-1&SortDirection=Descending
*March 8, 2015*

**Physics**

at (0,0) the fields from the first two charges cancel each other. to get a field at (0,0) in the y direction the x components of charges Q must cancel. Therefore one must be +Q and the other -Q If the field is up (+ i direction) the one below the axis is +Q and the one above ...
*March 8, 2015*

**so what did you get ?**

I already did this stuff in school. It is your turn to try. I suspect someone will check your results.
*March 8, 2015*

**Math Functions**

p = R - C = 5 x^2 + 19 x - 10 where is that zero? solve quadratic x = [ -19 +/- sqrt (361+200) ]/10 = [ -19 +/- 23.7 ]/10 = .469 thousand = 469
*March 8, 2015*

**Physics**

initial speed up Vi = 21 sin 37 v = Vi - 9.81 t at top v = 0 so t = ( 21 sin 37 ) / 9.81 = time rising time falling = time rising so 2 t = time in air
*March 8, 2015*

**math**

If only integer sides 1 , 10 , 1 nope sum of two must be > third 5 , 4 , 3 sure one 4 , 4 , 4 sure two 3, 3, 6 , nope, straight line 2 , 5 , 5 sure three 2 , 4 , 6 nope you found a fourth ?
*March 8, 2015*

**math**

do they have integer lengths? if so 2,5,5 4,4,4 5,4,3
*March 8, 2015*

**math**

Google Heron's formula Area^2 = A^2 = S(S-a)(S-b)(s-c) where S = (1/2) perimeter = 6 here so A^2 = 6 (6-a)(6-b)(6-c) so look for maximum of (6-a)(6-b)(6-c)
*March 8, 2015*

**physics**

It slows down, shorter wavelength, same frequency (note it can not change frequency. There is no storage of waves, the same number have to pass a given point per unit time on each side.) lambda = V * T so lambda = V/f if V goes down/ lambda goes down
*March 8, 2015*

**College Math**

e^rt = e^(.062*7) = 1.543418868 times $ 2600 = $ 4012.89
*March 8, 2015*

**Maths**

if you mean in radians 55 deg * (pi rad/180 deg) .9599 radians
*March 8, 2015*

**physics**

Every turn you go one circumference, 2 pi R
*March 8, 2015*

**physics**

must know radius R C = 2 pi R so 500 * 2 pi R
*March 8, 2015*

**Algebra 2**

if so then 5 -2.5 sqrt 3 + 2.5 i -2.5 sqrt 3 - 2.5 i
*March 8, 2015*

**Algebra 2**

x^3 = 125 x = 5 works you do not say if you also do complex numbers
*March 8, 2015*

**physics**

40 * 5 60 * 5 * 0.40 Joules
*March 7, 2015*

**physics**

force down = m g = 63*9.81 N mass accelerated = 63+10 = 73 kg a = F/m = 9.81 (63/73) m/s^2
*March 6, 2015*

**Social Studies**

Although the astrolabe has origins traced back over 1,500 years, it was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (Andalusia) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it...
*March 6, 2015*

**linear programming - suspect not correct problem statement**

x = paper y = cans p = 500 x + 350 y y </= 200 x </= 200 x >/= 10 y >/= 80 I do not understand last constraint, redundant if y</=200 rectangle corners at (10, 80) (10,200) (200, 80) (200,200) well, go ahead and evaluate p at each corner but obviously mas at (...
*March 6, 2015*

**algebra**

6, 12, 18, 24 is 4 4/24 = 1/6 1 - 1/6 = 5/6 permutations of 12 things 4 at a time is n!/(n-r)! = 12!/8! = 12 * 11 * 10 * 9 = 11,880 if it is a number I would call it quatitative.
*March 6, 2015*

**Math**

B 5 to 15 is one to three not one to five C 3/5 = painting/sculpture so 3/8 = painting/total 5/8 = sculpture/total 3/8 * 24 = 9 5/8 * 24 = 15
*March 3, 2015*

**maths**

45 = 5*3*3 60 = 5*3 *2*2 so we need 5*3*3*2*2 = 180
*February 28, 2015*

**Physics**

North: 4 + 1.2 sin 35 East 1.2 cos 35 + 1.3
*February 28, 2015*

**Math**

That seems to work.
*February 28, 2015*

**Physics**

Vi = 26.5 sin 30.9 = 13.6 v = Vi - g t at top v = 0 9.81 t = 13.6 at top t = 1.39 seconds up u = 26.5 cos 30.9 u = 22.7 d = u t = 22.7*1.39 = 31.6 meters
*February 28, 2015*

**Physics**

Weight does not matter. v = sqrt (2 g h)
*February 27, 2015*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*February 27, 2015*

**Vocabulary**

We could calculate it all right. It was so lethargic it was frigid.
*February 27, 2015*

**Chemistry Need Help**

You only have 1.50 mol of Cl2 so you are only going to get 3.00 mol of ClF You have 0.25 mol of excess F2 left over.
*February 27, 2015*

**Math**

prob of not getting=(1 - prob of getting) (not getting)(not getting)(getting)
*February 27, 2015*

**algebra**

235 - 15 x = 55 15 x = 235 - 55 15 x = 180 x = 12
*February 26, 2015*

**Math**

u dot v = |u||v| cos T |u| = sqrt(9+4) = sqrt 13 |v| = 4 u dot v = 12 + 0 = 12 so 12 = 4 sqrt(13) cos T cos T = .832 T = 33.7 degrees do the second one the same way
*February 24, 2015*

**Vectors: A car travels 59.5 miles then makes a 90°**

I thought I did it your way :) All I did was get the angle, you got the distance (hypotenuse)
*February 24, 2015*

**Vectors: A car travels 59.5 miles then makes a 90°**

53 + 56.6 counterclockwise from west or 109.6 which is 109.6 - 90 = 19.6 degrees east of South
*February 24, 2015*

**Vectors: A car travels 59.5 miles then makes a 90°**

the angle counterclockwise from west is 53 + tan^-1(90.3/59.5) that will end up in quadrant 4, east of south
*February 24, 2015*

**Vectors: A car travels 59.5 miles then makes a 90°**

But good job so far Hanky.
*February 24, 2015*

**Vectors: A car travels 59.5 miles then makes a 90°**

Remember it did not just ask for distance (scalar) but also direction (vector).
*February 24, 2015*

**Science**

You are welcome. Now remember how I did that because there is much confusion. If we were only in a satellite looking down on it, it would be easy :)
*February 24, 2015*

**Science**

I do not know if you know about conservation of angular momentum so will assume not. imagine a low over New York. I particle of air from up around Albany is drawn South to the low. HOWEVER The particle was moving east with the surface of earth toward the sunrise at some speed ...
*February 24, 2015*

**Algebra 1**

You are welcome again :)
*February 24, 2015*

**Algebra 1**

2 y = x + 6 2 y = x + 6 identical, same line, infinite solutions x + 7 y = 34 x + 7 y = 32 parallel lines, never cross, no solution
*February 24, 2015*

**maths typo maybe ?**

Why would you buy 4 times as many pizzas as drinks ??? anyway p = 4 d 112 = 12 p + .5 d so 112 = 48 d + .5 d 112 = 48.5 d d = 2.31 p = 111 I am sure you have this backwards d =
*February 24, 2015*

**Mathematichs concepts**

I am inclined to agree with you.
*February 24, 2015*

**Algebra 1**

You are welcome.
*February 24, 2015*

**Algebra 1**

4y +3 = 3y +x is y = (x - 3) then 2 x + 4 (x-3) = 18 6 x - 12 = 18 6 x = 30 x = 5 etc
*February 24, 2015*

**typo ?**

does not look right, -x^1 ?
*February 24, 2015*

**algebra**

(2x+1)(x+2) = 2 x^2 + 5x + 2 sure enough That is the way to check it without bothering to ask us :)
*February 24, 2015*

**algebra**

w = A/L w = (2 x^2 - 11 x + 5)/(2 x - 1) = (2x-1)(x-5) / (2x-1) = x-5
*February 24, 2015*

**Chemistry Honors**

R = 62.4 L Torr K−1 mol−1 T = 273 + 25 = 298 K n = 2 mol V = 10.4 L and P = n R T/V = 2 * 62.4 * 298 / 10.4
*February 24, 2015*

**Earth Science to Ms.Sue (urgent )**

The Cenozoic is sometimes called the Age of Mammals, because the largest land animals have been mammals during that time.
*February 24, 2015*

**Earth Science to Ms.Sue (urgent )**

http://www.google.com/search?q=cenozoic+era&ie=utf-8&oe=utf-8
*February 24, 2015*

**Earth Science to Ms.Sue (urgent )**

https://www.google.com/search?q=cenozoic+era&ie=utf-8&oe=utf-8
*February 24, 2015*

**algebra**

(t-8)(t+1)
*February 24, 2015*

**algebra**

x^2 + x - 6 = (x-2)(x+3) divide that by (x-2) and you get (x+3) :)
*February 24, 2015*

**Algebra**

Hey, that looks like the last one I did (x+1)(x-4) / (x+1) = x-4
*February 24, 2015*

**Physics**

average speed = .25 mi / 5.2 s so top speed = 2 * average speed if a is constant so Vf = .5 mi /5.2 s if you want that in mi/h multiply by 3600 s/h so Vf = 346 miles/hour Vf = a t .5/5.2 = a (5.2) a = .01849 miles/s^2 makes more sense if in feet/s^2 multiply by 5280 feet/mile ...
*February 24, 2015*

**math**

x^2 + x - 2 - x^2 + 6x - 9 7 x - 11
*February 24, 2015*

**math**

17 is a prime number so the LCD is 21*17 = 357 11/21 * 17/17 = 187/357 9/17 * 21/21 = 189/357 189 is bigger than 187
*February 24, 2015*

**Math - Algebra 1**

3.6 /12 = monthly interest rate = r b(t) = 9000 (1 + r)^12t c(t) = 40*12 t C(t) = 9000 (1 + r)^12t + 40*12 t
*February 24, 2015*

**physics**

when the angle is in quadrant II 53.4 degrees left of north then east component is - sin then north component is + cos if you want the angle from the x axis then it is 90 - 53.4 = 36.6 then you could use cos and sin like you want because sin (90-x) = cos x cos (90-x) = sin x :)
*February 24, 2015*

**Typo**

copied your result, should be I CLAIM Beta-subX = -3.20 ft SIN(53.4) = -2.56 Beta-subY = 3.20 ft COS(53.4) = 1.90
*February 24, 2015*

**physics**

Because the angle 53.4 is left from the Y axis, not up from the X axis. They tricked you with the west of north that is left of the Y axis DRAW the picture.
*February 24, 2015*

**physics**

This is right: Alpha-subX (for the x component) Alpha-subX = 81.6 ft * cos(31.7) = 69.426 Alpha-subY (for the y component) Alpha-subY = 81.6 ft * sin(31.7) = 42.878 This is WRONG Beta-subX = 3.20 ft cos(53.4) = 1.907 Beta-subY = 3.20 ft sin(53.4) = 2.569 I CLAIM Beta-subX = -3...
*February 24, 2015*

**physics**

But going west is NEGATIVE x
*February 24, 2015*

**physics**

Yes, exactly BUT THE SECOND ONE was west of north x distance = 69.4 -3.2 sin 53.4 = x y distance = 42.9 + 3.2 cos 53.4 = y d = sqrt (x^2 + y^2) tan of angle north of east = y/x
*February 24, 2015*

**Physics**

the mass is proportional to the number of mols n2/n1 = m2/m1 P1 V1 = n1 R T1 so n1 = P1 V1/R T1 P2 V2 = n2 R T2 so n2 = P2 V2/R T2 n2/n1 = m2/m1 = (P2 V2/P1V1)(T1/T2) 6/4.9 = (P2*2/75*5)(323/273) solve for P2
*February 24, 2015*

**physics**

in one revolution the tire goes 2 pi r = pi D feet = pi (2) feet which is (2 pi/5280)miles (2 pi/5280)n = 60,000 miles (part b) 2 pi n = number of radians (part a)
*February 24, 2015*

**Algebra**

x > y x + y = 6 x - 2 y = 9 ------------subtract 0 + 3 y = -3 y = -1 x = 7
*February 23, 2015*

**algebra**

The volume of anything pointy with straight sides is (1/3) base area * height V = (1/3)(pi)(25)^2 (7.2) same V for second one (1/3)(pi)(25)^2 (7.2)=(1/3)(pi)(15)^2 h so 625 (7.2) = 225 h h = (625/225)(7.2) In fact you never even need pi
*February 23, 2015*

**physics**

If A stopped and it was elastic then the B has the same as A had (1/2)(.55)(v^2)
*February 23, 2015*

**algebra**

Move right five 8.9 * 10^-5 move left two 4.56981 * 10^2 Due to your lack of showing your attempt I can not tell why you were having trouble with this.
*February 23, 2015*

**Science**

.9189189189..... But some of the ice floats above the water. Something must be holding it below water.
*February 23, 2015*

**Electricity and magnetism**

but the force decreases with distance as 1/x^2 F = k/x^2 we want W = integral F dx from x = d1 to x = d2 W = k integral (dx/x^2) = k (-1/x) from x = d1 to x = d2 = k/d1 - k/d2
*February 23, 2015*

**maths**

each year p(y) = .92 p(y-1) when y = 0, p = 5300 when y = 1, p = .92 * 5300 when y = 2, p = .92*.92 * 5300 when y = n, p = .92^n * 5300 think compound negative interest :) p = .92^y * 5300
*February 23, 2015*

**Math**

Yes, any real x except x = 1
*February 23, 2015*

**calculus**

aaaarrrrrgggggghhhhh !!!!
*February 23, 2015*

**calculus**

I will just do two dimensions for demo a) A dot (B+C) = AxBx + Ax Cx + AyBy + AyCy does that equal AxBx+AyBy + AxCx+AyCy Yes, it does b) A X (B+C) = A X (Bx+Cx)i +(By+Cy)j i j k Ax Ay 0 (Bx+Cx) (By+Cy) 0 find determinant [Ax(By+Cy) - Ay(Bx+Cx) ]k k direction of course [ AxBy...
*February 23, 2015*

**physics**

LOL - That same old impulse thing again. find change of momentum = final m v - initial mv (doing only component perpendicular to wall, v = 10 sin 60 inbound v = - 10 sin 60 outbound change in v = 2 * 10 sin 60 Force = change in momentum/time It only acted perpendicular to the ...
*February 22, 2015*

**chemistry**

22.41 - 21.30 = 1.11 mL so 8.7 g/1.11 mL = 7.838 g/mL or g/cm^3 almost 8 times density of water by the way which is how you remember it.
*February 22, 2015*

**ap physics**

I can not see your graph but use the logic from the other problem I just helped you with. F = m a = m dv/dt impulse = integral F dt = final mv - initial m v
*February 22, 2015*

**AP physics**

Force = change in momentum/time = m a when m is constant so Force * time = change of momentum, called impulse impulse = force * time = change of momentum final momentum = .278 (22.4) initial momentum = .278 (-16.2) change = .278 (22.4 - {- 16.2} ) = .278 (38.6) = 10.7 kg m/s (...
*February 22, 2015*

**math**

sure enough :)
*February 22, 2015*

**math**

x [(102 x - 228 )/6] +51 = 200 (102 x - 228 )/6 = 149 102 x - 228 = 894 102 x = 1122 x = 11
*February 22, 2015*

**Calculus**

the extrema of a function are where the derivative is zero or at the ends of the domain concave or convex depends on sign of second derivative at that extreme. If plus, it holds water (minimum). If negative, it sheds water (maximum).
*February 22, 2015*

**physics**

I assume they gave you mu dry and mu wet Ac = v^2/R = v^2/30 inward force needed = m Ac = m v^2/30 max inward force provided = mu m g so v^2 = 30 mu g
*February 22, 2015*

**finite math**

prob of red, white then blue = 4/13 * 6/12 * 3/11 prob of red, blue then white = 4/13 * 3/12 * 6/11 prob of white, red then blue = 6/13 * 4/12 * 3/11 prob of white, blue then red = 6/13 *3/12 * 4/11 prob of blue, red then white =3/13 * 4/12 * 6/11 prob of blue, white then red...
*February 22, 2015*

**Math Help!**

Oh well, number 2 start at 1 for min 1 + 2 + 3 + 4 ..... = 45 arith series (n/2)[2 + (n-1)(1)] = 45 n + (n/2)(n-1) = 45 n + n^2/2 -n/2 = 45 n + n^2 = 90 n^2 + n - 90 = 0 n = [ -1 +/- sqrt(1+360) ]/2 n = 18/2 = 9 check 1 + 2 + 3 + .....9 = 4.5(2+8) = 45 sure enough
*February 22, 2015*

**Physics**

Answer g) first (trick question) F = m a a = 0 so net force on crate = 0 =========================== a) 1 - friction 2 - m g gravity 3 - normal from ramp so three b) gravity, just one c) none are horizontal d)gravity, normal and friction all have vertical components so three e...
*February 22, 2015*

**Physics**

up is + a) gravity force down = weight = -m g = -1210*9.81 = -11870 N b) F is positive up F = m a = 1210(-1.4) F = - 1696 N c)gravity pushing down, helicopter pushing up d)lift is up lift - 11870 = m a = -1696 lift = 11870 - 1696 = 10176 N up
*February 22, 2015*

**Vectors Math**

Your notation is a mystery to me. The magnitude of the projection of A on to A is |A| cos T where T is the angle between A and B but |A| cos T = |A| |B| cos T /|B| which is A dot B /|B| Now we need a unit vector in direction B That is B/|B| so in the end we need A dot B * B /|...
*February 22, 2015*

**Vectors**

"bearing" means what direction you LOOK. "heading" means what direction you point the vehicle. As in: We were heading north when we took a bearing of 90 degrees on a lighthouse east of us.
*February 22, 2015*

**Vectors**

Math teachers do not know navigation English. It drives me crazy. You do not head on a bearing. You sail or fly on a heading. the plane is flying on a heading of 200 (about SSW) at 400 km/h the plane is also moving at 100 km/h southwest which is 180+45 = 225 degrees You can do...
*February 22, 2015*

**Physics**

C = q/V so V = q/C so q1/C1 + q2/C2 + q3/C3 = 58 but q1=q2=q3 becaue where else are the electrons to come from or go to? so 1/C1 + 1/C2 + 1/C3 = 58/ q 10^6 (1/3.83+1/5.89+1/12.9 = 58 /q 10^6 (.508) = 58 / q q = (58/.508)10^-6 V = (58/.508)/3.83 = 29.8 volts
*February 21, 2015*

**College Physics**

900(1.0)+ Tright(3) so Tright = 300 N Tright + Tleft = 900 so Tleft = 600 N
*February 21, 2015*

**college physics**

been there, done that, see above
*February 21, 2015*

**Physics**

C = q/V so V = q/C so V = qA/CA = qB/CB and E = (1/2) q V = (1/2) C V^2 5.7*10^-5 = (1/2)(17*10^-6)V so V = 6.71 volts then 6.71 = (qB/6.9)10^6
*February 21, 2015*

**physics**

A steel ball with a mass of 0.65 kg is swinging in a circle with a radius of 1.3 meters at a speed of 17m/s. What is the centripetal force?
*February 20, 2015*