Thursday

September 3, 2015
Total # Posts: 21,879

**physics**

v = Vi - 9.81 t if it came down at 28 m/s, it started up at 28 m/s (symmetry) v = 28 - 9.81 t at the top, v = 0 0 = 28-9.81 t so t = 28/9.81 at the top, same time falling h = (1/2)(9.81) t^2 h = (4.9)(28/9.81)^2 h = 4.9
*February 5, 2015*

**math - We do not do magic**

If you do not give some sort of distribution of customer arrival times I have no idea when Tony's staff should be there.
*February 5, 2015*

**math Huh ?**

I do not have the slightest idea what you are talking about. Arithmetic sequences or series maybe ?
*February 5, 2015*

**physics**

Now you should be able to do them.
*February 5, 2015*

**physics**

in general if speed is s at A degrees above horizontal u = s cos A Vi = s sin A
*February 5, 2015*

**physics**

Now divide your problems up into vertical problems and horizontal problems if horizontal speed is u at start it is u to the finish so x = u t if initial vertical speed is Vi then v = Vi - 9.81 t (remember v=0 at top) h = Hi + Vi t - 4.9 t^2
*February 5, 2015*

**physics**

just a vertical problem Vi = 17.9 sin 36.0 h = 0 + Vi t - 4.9 t^2 0 = 0 + t (Vi - 4.9 t) so it is at ground level at t = 0 of course and at t = Vi/4.9
*February 5, 2015*

**Algebra typo ???**

a (b+c) = db a (b+c) = dc If you did not make a mistake than of course b = c but CHECK FOR TYPOS
*February 5, 2015*

**physics**

first do the horizontal problem with constant horizontal speed of 13 for 21.4 m to get time in air distance = speed * time t = 21.4 /13.0 now we know it fell for time t h = (1/2) g t^2 h = (1/2) (9.81) (21.4/13.0)^2 meters
*February 5, 2015*

**Math**

Not that I know of.
*February 5, 2015*

**Math**

(5/12) s = 10 c + 20 (7/12) s = 15 c well we have two linear equations with two unknowns. We can do it. 7 s = 180 c so c = (7/180) s (5/12) s = (7/18)s + 20 (5/4) s = (7/6) s + 60 (15/12)s = (14/12) s + 60 s/12 = 60 s = 720 kg
*February 5, 2015*

**physics**

speed east = 1.65 cos 18.8 t = 21.0 / ( 1.65 cos 18.8 )
*February 5, 2015*

**Maths**

5 f + 10 t = 500 f + t = 90 f + 2 t = 100 f + 1 t = 90 ------------- subtract t = 10 then f = 80 check 400 +100 = 500 80 + 10 = 90 ok
*February 5, 2015*

**chm**

water is 1 g/mL so we have 0.105 g of H2SO4 per mL How many mols is that H2 = 2 g/mol S = 32 g/mol 4 O = 64 g/mol total = 98 g/mol .105/98 = .0011 mol /mL which is 1.1 mol/Liter
*February 2, 2015*

**Math**

4 * (13/5) = 10.4 which is more than 10
*February 2, 2015*

**math**

Oh, sorry, assumed that if you were deciding what was a function you also were doing inverses of functions. You will be :)
*February 2, 2015*

**math**

Just watch out if you are asked for the inverse next.
*February 2, 2015*

**math**

It IS a function ! (I said that)
*February 2, 2015*

**math**

there is only one value of y for every x so it is a function (a parabola in fact) The inverse of this however is NOT a function
*February 2, 2015*

**Physics**

Gravity is not in this because it says in a HORIZONTAL circle (it must be on a table top or something but 625 is much bigger than g anyway))
*February 2, 2015*

**Physics**

Your problem only has two significant figures accuracy to two significant figures w = 25 so r w^2 = 625 F = m a F = 2 kg * 625 m/s^2 = 1250 N
*February 2, 2015*

**money**

1 small + 1 medium = $20 so $60 left we can only buy one large for $32 60 = 32 = $28 left (3 bought so far) One medium for 16 leaves 12 (4 so far) finally 3 smalls leaves $0 (7 total)
*February 2, 2015*

**4th grade math fraction**

4 * 6 = 24 juice boxes gave away 2 * 3 = 6 24 - 6 = 18 are left
*February 2, 2015*

**5th grade math**

to divide fractions invert the one on the bottom and multiply (8/11) / (4/1) = (8/11)(1/4) = 2/11 (3/8)(10/3) = 10/8 = 5/4 = 1 1/4 (6/1)(4/3) = 24/3 = 8 (1/6)(6/5) = 1/5 etc etc etc
*February 2, 2015*

**algebra**

5 b (6b+5) + 6 (6b+5) = (5b+6)(6b+5)
*February 2, 2015*

**algebra**

no (s + 7)(s - 4 )
*February 2, 2015*

**algebra**

********2 b + 8 (b-3) | 2 b^2 + 2 b - 9 ********2 b^2 - 6 b ------------------------ ************** + 8 b - 9 ************** + 8 b - 24 ------------------------- *****************R = + 15 In other words I suspect you have a typo or you have a remainder of 15
*February 2, 2015*

**maths please help**

x^2 = 2 x = +/- sqrt 2 2. not sure what is denominator 3. x^2/2 + 6 x + 10 = 0 x^2 + 12 x + 20 = 0 (x+10)(x+2) = 0 x = -10 or x = -2 4. x^2 - 7 x = 0 x (x-7) = 0 x = 0 or x = 7
*February 2, 2015*

**Science**

The jellyfish, which I suspect is actually a squid (I gather your teacher is not a fisherman), moves forward as the water moves aft. I suppose you could say that this is due to the third law (action---> equal magnitude opposite direction reaction). However I consider this a...
*February 1, 2015*

**Physics**

F = k Q1 Q2 /d^2 due to right one, +force because opposite sign due to middle one, -force because of same sign F = k(10^-6)(10^-6)(65) [ 95/1.2^2 -48/.6^2 ]
*January 31, 2015*

**Physics**

force up = 25 sin 25 force down = 5(9.81) normal force = 5(9.81) - 25 sin 25 pull force = 25 cos 25 back friction force = 4 so 25 cos 25 - 4 = 5 * a
*January 31, 2015*

**Physics**

force up from left wire = 106 sin 5 force up from right wire also 106 sin 5 total force up = 212 sin 5 = weight down = m g = 9.81 m m = (212/9.81)sin 5
*January 31, 2015*

**physics**

u = speed * cos 27.1 7.72 = speed *cos 27.1 * t where t is time in air h = Hi + Vi t - (1/2) g t^2 0 = 0 + speed*sin 27.1 * t - 4.9 t^2 but we know t = 7.72/(speed*cos 27.1) call speed s 0 = 0 + 7.72 tan 27.1 - 4.9*7.72^2/(s^2cos^227.1) solve for s do it again for s = 1.05 s
*January 31, 2015*

**math**

j = dan + 30 dav = 3 j j + dan + dav = 400 (dan+30) + dan + 3 (dan+30) = 400 5 dan + 120 = 400 5 dan = 280 dan = 56 j = dan + 30 = 86 dav = 3 j = 258
*January 31, 2015*

**arithmetic not vector calculus**

p = 3000 q1 + 12000 q2 - 5000
*January 31, 2015*

**math**

It moved up from -7 to +7 so it could be a translation straight down. It could also be a reflection about the x axis, but the question asks for a "translation".
*January 31, 2015*

**georgia state history**

salt or pepper?
*January 31, 2015*

**Trigo**

Angle ABP = 54 - 46 = 8 Angle PBQ = 90- 54 = 36 (note used 54) so Angle PAB = 180 - 8 - 36 = 136
*January 31, 2015*

**math**

huh? 78/100 = 39/50
*January 31, 2015*

**algebra**

n = o + 9 o + (4/5) n = n so n - 9 + 4 n/5 = n 4 n /5 = 9 4 n = 45 n = 45/4 o = 45/4 - 36/4 = 9/4 ============================ now check n = o + 9 = 9/4+36/4 = 45/4 yes o + (4/5) n = n 9/4 + (4/5)(45/4) = n ? 5*9/4 = n ? 45/4 = n yes
*January 31, 2015*

**algebra**

Just did that, see above
*January 31, 2015*

**Maths Problem**

[ a+b ]/2 = 81 so a+b = 162 but b = a+26 so 2 a + 26 = 162 2 a = 136 a = 68
*January 31, 2015*

**physics - question incomplete**

Force on what ? do you mean in a row, each 20 cm from the previous ? In general F = k Q1 Q2/d^2 toward each other if opposite sign repel each other if same sign
*January 31, 2015*

**Natural science**

Hummm, my thing is physics so I am not sure. However I would Google pistel and stamen yes, try this: http://urbanext.illinois.edu/gpe/case4/c4facts1a.html
*January 31, 2015*

**MATHS**

http://www.jiskha.com/display.cgi?id=1422706001
*January 31, 2015*

**Calculus**

Do it Reiny's way (but mine is more fun)
*January 31, 2015*

**Calculus**

2.44 + .0053535353 ....... 2.44 + (1/100)(.53535353 .... ) .53535353... = .53 + .53/100 + .53/100^2... = a + a r + a r^2 + a r^3..... where a = .53 and r = .01 sum of that infinite series = a/(1-r) so .53 /(.99) = 53/99 so we have 2.44 + (1/100)(53/99) (1/100)( 244 + 53/99) I ...
*January 31, 2015*

**Statiatics**

4/5 is chance wrong problems are independent so (4/5)(4/5) = 16/25
*January 31, 2015*

**math**

independent probabilities (1/42)(1/47)
*January 31, 2015*

**Trigo**

you went a total of 160 straight north you went 40 east draw that on a graph, 40 right, 160 up the angle between north and east is 90 deg so you want the hypotenuse of that right triangle.
*January 31, 2015*

**Trigo**

y distance = 90 + 70 = 160 x distance = 40 want hypotenuse d = sqrt (40^2 + 160^2)
*January 31, 2015*

**Calculus**

e^.2x = 75/(30*16) .2x ln e = ln (75/480) but ln e = 1 .2 x = ln (75/480) ======================= 8^tan x * ln 8 * (1/sec^2 x)
*January 31, 2015*

**Physics - must know all masses**

insufficient information
*January 30, 2015*

**Physics**

F = G Mearth Moject / r^2 F1 = G Mearth m/6400^2 F2 = G Mearth m/6780^2 so F2/F1 = (6400/6780)^2 = 0.891
*January 27, 2015*

**math**

150 C (95-0) = 21 (heat of fusion of ice) where C is heat capacity of iron about 0.450 J/ g deg c
*January 27, 2015*

**Math - Problem solving**

last year = x this year = x+20 x = 0.75(x+20)
*January 27, 2015*

**COMBINED OPERATION ON FRACTIONS**

(3/5)j +(3/4)(2/5)j + 3 = j
*January 27, 2015*

**physics**

both angular and linear momentum are conserved. The center of gravity of the system is height: h (m+m) = m x + m (L/2) and it is moving at speed Ucg (m+m) = u m then of course you have the rotation about the cg
*January 27, 2015*

**Math**

the area of the base is easy w*L if the height is h then two of the slope triangles have base w and height along the slope of sqrt(h^2 + L^2/4) so the sum of those two triangle areas is w *sqrt(h^2 + L^2/4) similarly the sum of the other two triangle areas is L * sqrt (h^2 + w...
*January 27, 2015*

**Math / Algebra**

I agree
*January 27, 2015*

**algebra**

-y = 18 * 7 y = -18 * 7
*January 27, 2015*

**Math word problems**

100 - 25 = 75 so you took 25 off every hundred In other words, 25% discount another way to do it: 160 - 120 = 40 dollars discount 100 (40/160) = 25 %
*January 27, 2015*

**Science**

If you look at the inside of a tree branch or tap maple sap you see straw like tubes that transport fluid around.
*January 27, 2015*

**Physics - Vectors**

|A| |B| cos theta = A dot B 2.2 * 10 * cos theta = 14 theta = cos^-1 (14/22) theta = 50.5 degrees
*January 26, 2015*

**Math**

x = 2log4 y log4 y = (x/2) 4^log4 y = 4^(x/2) y = 4^.5x
*January 21, 2015*

**math**

1.75 inches ( 45 miles/2.25 inches) =
*January 21, 2015*

**physical**

(1/2)m v^2 = m g h so v = sqrt (2 g h) remember that
*January 21, 2015*

**physics**

Google Millikan oil drop experiment for example: http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Ryan_McAllister/Slide3.htm
*January 21, 2015*

**math**

the absolute value of (sec x)^2 is just sec^2 x because when you square a number it is positive so we have (1/cos^2) sin / [1/sin] or tan^2 x dx = tan x - x + c
*January 19, 2015*

**physics**

calculate F = Q E do a = F/m to get a, the acceleration then plain old constant acceleration x = (1/2) a t^2
*January 19, 2015*

**Civics**

YES !!!!!
*January 19, 2015*

**Civics**

Google Marbury vs Madison
*January 19, 2015*

**Physics**

x = 2 + 3.2 t - 3.85 t^2 when is v = 0? dx/dt = v = 3.2 - 7.7 t v = 0 when t = 3.2/7.7 = .416 seconds then x = 2 + 1.33 - .665 = 2.66 If you do not know calculus, find the vertex of the original equation.
*January 19, 2015*

**Physics**

d = Vi t + (1/2) a t^2 98.3 = 29 t - 1.8 t^2 1.8 t^2 -29 t + 98.3 = 0 solve quadratic for t [ 29 +/- sqrt ( 841 - 708) ] /3.6 [ 29 +/- 11.5 ] / 3.6 = 4.86 (ignore the big time, it is on the way back :)
*January 19, 2015*

**Civics**

14 says they have the right to go to school just as other citizens do. 13 just says they are not slaves any more.
*January 19, 2015*

**Civics**

I would say 14 which does not allow sates to deny privileges to any citizens.
*January 19, 2015*

**ap calc**

(z^2)^(1/2) = z you have (x^2 - 4) dx x^3/3 - 4 x + C
*January 19, 2015*

**Math**

I am an engineering teacher not a civics teacher jeje.
*January 19, 2015*

**Math**

(4/5)(7/8) = 7/10
*January 19, 2015*

**Algebra**

s = side length x = long length 2 s + x = 1600 so x = (1600-2s) 2 s (5) + x (20) = 13,000 10 s + 20 (1600-2s) = 13,000
*January 19, 2015*

**physics**

By the way to do the second one you must know the density of the fluid. These are very strange questions. Are you sure you have copied them correctly?
*January 19, 2015*

**physics**

I do not know. All I know is the ratio of areas. 80 (pi r^2) = 1300 (pi R^2)
*January 19, 2015*

**SCIENCE**

3. An electric engineer might (1 point) Build a dam to provide a source of hydroelectric power.*** Develop new fuels to use in the next generation of fuel-efficient cars. Design a remote-controlled toy race car. Design an airplane wing that changes shape to increase stability...
*January 19, 2015*

**Physics**

at the same acceleration as (one g about 9.8 m/s^2)
*January 19, 2015*

**physical science**

------>------> = ------------> <----- ------> = 0
*January 19, 2015*

**physics**

F * d = work done by friction = initial Ke = (1/2) m v^2 F * 50 = (1/2)(750)(900) 100 F = 750 * 900 F = 750 * 9 There are harder ways of course using F = change of momentum/ time = 750*30/t then 50 = (1/2)a t^2 where a = 30/t so 100 = 30 t t = 10/3 seconds to stop a = 9 m/s^2...
*January 19, 2015*

**Physics**

56.1 mi/h = 25.1 m/s v = Vi - a t 0 = 25.1 - a t so t = 25.1/a d = (1/2) a t^2 206 = a t^2 206 = a(630/a^2) = 630/a a = 3.06 m/s^2 (negative of course)
*January 19, 2015*

**Physics**

h = (1/2) g t^2 = 4.9 (3.12)^2
*January 19, 2015*

**Physics**

d = (1/2) a t^2 194 = 6.60 t^2 solve for t then v = Vi - 6.60 t = 0 at end Vi = 6.60 t
*January 19, 2015*

**Physics**

v = Vi + a t 104/3.6 = 74/3.6 + 1.52 t
*January 19, 2015*

**ap calc**

d/dx (2x+7)) = 2 so the 1/2 gets rid of the 2
*January 19, 2015*

**Physics**

but you forgot the work done against gravity m g * 500 = .05 * 9.81 * 500 = 245 J 1450 - 245 = 1204 J so 1204 = .05 * a * 500 =============================== The second one looks ok
*January 18, 2015*

**physics**

Aaaarrrgghhhhh !!!!! Joey is right. At the top v = 0, no velocity except that of mother earth spinning on her axis and making her way around the sun. The acceleration is constant, -9.81 m/s^2 the whole time. Charlie could not possibly, any way, be more wrong. Send him to his ...
*January 18, 2015*

**Physics**

t = 4.2 T = 8 a = 5 I guess it started from a dead stop. x = (1/2) a t^2 during acceleration Vi = speed at end of acceleration = a t X = Vi T during constant speed so distance = (1/2) a t^2 + Vi T
*January 17, 2015*

**Math**

32 = 8 * 4 56 = 8 * 7 so 32 + 56 = 8 (4+7)
*January 15, 2015*

**MATH**

how much of the 40 hours he works at each job
*January 15, 2015*

**Torque**

Huh? 30 * 1.5 = 45 BUT 60 * 1 = 60
*January 15, 2015*

**physicsss**

You are welcome.
*January 15, 2015*

**physicsss**

If the velocity is constant you are correct.
*January 15, 2015*

**Physics**

work done in stopping = brake force * 75 meters (1/2) m v^2 = work done by brakes (1/2) m (93)^2 = F * 75 F = m (57.66) but F = ma so a = 57.66 that is the acceleration the tires can give you. Use it for centripetal acceleration a = 57.66 = v^2/r r = (93)^2/57.66
*January 15, 2015*