Thursday

October 27, 2016
Total # Posts: 27,573

**Physics**

dx/dt = 6 t^2 - 42 t + 60 = 6 (t^2 - 7 t + 10) = 6 (t-2)(t-5) negative from 2 to 5 (Not 3 to 5)

*February 9, 2016*

**Calculus**

c = cups/day p = pennies/cup dc/dp = -2/5 so c = -(2/5) p + constant when p = 50, c = 40 so 40 = -2*50/5 + constant constant = 60 and c = -(2/5) p + 60 now you can make that p = 5n if you choose where n is an integer number of nickels c = -2 n + 60

*February 8, 2016*

**physics**

Now I did the grasshopper, same deal

*February 8, 2016*

**physics**

h = Vi t - 4.9 t^2 .587 = Vi t - .5*9.81 t^2 but t at top is Vi/9.81 where 0 = Vi - g t .587 = Vi^2/9.81 - .5 * 9.81 (Vi^2/9.81^2) .587 = .5 * Vi^2/9.81 Vi = 3.39 m/s vertical up Vi = speed * sin 58 so speed = 4.00 m/s part a u = 4.00 cos 58 = 2.12 m/s time in air = 2 * rise ...

*February 8, 2016*

**Math**

out of n, n-6 were gotten right so let's find n-6 Jack alone got 40 -32 = 8 Jill alone got 50-32 = 18 so in total alone they got 26 plus they got 32 together 26 + 32 = 58 right total plus the 6 wrong = 64

*February 8, 2016*

**maths**

every year multiply value by 0.90 1 year= 20,000 * .9 2 years 20,000 * .9^2 3 years 20,000 * .9^3 so part (c) n years 20,000 * .9^n It is like reverse compound interest, it will not go down 2,000 every year, but only 10% of its MOST RECENT value every year so 2 years 20,000...

*February 8, 2016*

**History**

Hey, that is pretty good. I am not a fan of his mother though.

*February 8, 2016*

**physics**

v at 10 m/s at t = 0 a = (final velocity-initial velocity)/time = (20 - 10)/5 = 2 m/s^2 so from (0,10) slope up = 2 m/s^2 to (5,20) from (5,20) to (25,20) horizontal from (25,20) to (35, 0 ) straight slope down (slope = -2)

*February 8, 2016*

**physics**

a = (final velocity -initial velocity)/time a = 49/16 m/s^2 weight = m g + m(49/16)

*February 8, 2016*

**maths**

looks like arithmetic sequence a = 3 d = 2 however sum of what terms?

*February 8, 2016*

**Physics**

now do A = F/m

*February 8, 2016*

**Physics**

Its acceleration will be in the direction of the net force Force horizontal component= Fh = 6.6*10^6 cos 47.5 Force vertical component = Fv = 6.6*10^6 sin 47.5 - 4.5*10^5*9.81 so Fh = 4.46*10^6 N Fv = 2.19*10^6 N F = sqrt(Fh^2+Fv^2) = 4.97*10^6 N tan A = Fv/Fh = 2.19/4.46

*February 8, 2016*

**Science**

eg: http://en.wikipedia.org/wiki/Lunar_mare

*February 8, 2016*

**Science**

1 a yes 2 b yes 3 a no b 4 c no d usually moon blocks sun light 5 a no c 6 d no b 7 a no c 8 b no a it all hits the other side 9 d no b 10 Google !!!! Hey - get yourself a light and a tennis ball and a soccer ball !

*February 8, 2016*

**Math Questions**

You are welcome.

*February 8, 2016*

**Math Questions**

2(9/3) = 2(3) = 6 yes 1 (18/6) = 1(3) = 3 yes 4 (10/5) = 4(2) = 8 yes

*February 8, 2016*

**Math Questions**

7(16/8) = 7(2) = 14 yes 6 (10/10) = 6(1) = 6 yes

*February 8, 2016*

**Math**

9.25% monthly .095/12 = .0079167 so every month multiply by 1.0079167 y = 1,000 (1.0079167)^(12x) now just activate your calculator :)

*February 8, 2016*

**Maths**

f(x,y) = 2 (x^2 + xy + 3 y + y^2) How could that be less than 0?

*February 8, 2016*

**typos**

Increases ?? from 15 m/s to 6 m/s ??? anyway a = (final velocity - initial velocity) / time d = Vi t + (1/2) a t^2 = 15 (20) + (1/2) a (400)

*February 8, 2016*

**maths**

a + (n-1) d second is a + d = 15 fifth is a + 4 d = 24 so a = 15 - d and (15-d) + 4 d = 24 3 d = 9 d = 3 then a = 12 so term n is 12 + (n-1)3

*February 8, 2016*

**Math Please help me and fast**

yes if you had 5 x = 0 for example, that would work for any old x and you would have infinite number of solutions. This is the opposite case.

*February 8, 2016*

**Math Please help me and fast**

0 x = 2 x = 2/0 undefined 4 y = 12 y = 3 b - 9 > 20 add 9 to both sides b > 29

*February 8, 2016*

**Math**

1. yes y = 100 (1/2)^(t/3) 2. looks good, divide by 2 every three days 3. I can not very well show you a graph maybe google graph exponential or graph A * B^-(kt) 4. 100 /(1/2)^3 = 100/(1/8) = 800 so yes but do not understand how you did it

*February 8, 2016*

**Algebra**

P = K D^2

*February 8, 2016*

**Physics**

F = k *stretch for each each supports 7.35 * 9.81/3 = 24 N 24 = k (.21) k = 115 N/m agree except you use 9.8 for g I suspect K = 3 k from part a = 343 omega = 2 pi f = sqrt(K/m) = 6.83 radians/s f = omega/2pi = 1.09 Hz T = 1/f = .919 seconds agree V = A omega sin (omega t) max...

*February 8, 2016*

**social studies**

My guess: The promises England had made to Palestinians.

*February 8, 2016*

**Probability**

Well, I guess about half of them 99,000 + 00,000 ? = 100,000 so I suppose about 50,000

*February 8, 2016*

**Physics**

a = (final velocity-initial velocity) / time a = (0 - Vi)/1.7 so a = -Vi/1.7 d = Vi t + (1/2) a t^2 50.7=Vi(1.7) -(1/2)(Vi/1.7)(1.7)^2 50.7 = (1/2)(1.7)Vi Vi = 59.6 m/s then a = - Vi/1.7 = -35.1 m/s^2 so F = m a = 13(-35.1) = - 456 N

*February 8, 2016*

**physics**

F1 horizontal T at 40 degrees from Vertical T cos 40 = m g T = 10 * 9.81 / cos 40 = 128 N F1 = T sin 40 = 128 sin 40 = 82.3 N

*February 7, 2016*

**Physics**

F on glider from spring = -kx beginning x = .1 meter potential energy in spring = kd^2/2 where d is extension = 5 d^2/2 = 2.5 d^2 = 2.5 (.1-x)^2 the potential energy at start = 2.5(.1)^2 = .025 Joules total the kinetic energy = (1/2)mv^2 = .1 (.2)^2 = .004 Joules so .025 = ....

*February 7, 2016*

**physics**

F = 1050 - 916 = 134 N UP a = F/m = 134/93.5 = 1.43 m/s^2 UP in other words his speed down is slowing

*February 7, 2016*

**physics**

I guess you mean maximum height of 100 m Vertical problem: Vi = 59 sin A v = Vi - 9.81 t at top v = 0 0 = Vi - 9.81 t so t = 59 sin A /9.81 at top 100 = Vi t - (9.81/2) t^2 100 = (59 sinA)^2/ 9.81 -(9.81/2) (59 sin a)^2/9.81^2 100 = (1/2)(59 sin A)^2/9.81 980*2 = (59 sin A)^2 ...

*February 7, 2016*

**physics**

We just need to do the vertical part of the problem. I assume it hit the ground where H = 0 Vi = 15 sin 35 = 8.6 m/s up H = Hi + Vi t - 4.9 t^2 0 = Hi + 8.6 (2.7) - 4.9 (2.7)^2 Hi = 12.5 meters

*February 7, 2016*

**physics**

You are welcome. I am sorry; I have no schedule (retired and doing a lot of other stuff).

*February 7, 2016*

**physics**

and tan angle = 22.2/16

*February 7, 2016*

**physics**

typo sqrt (22.2^2 + 16^2)

*February 7, 2016*

**but the horizontal speed?**

25 = 4.9 t^2 t = 2.26 seconds, yes v = Vi - 9.81 t v = -9.81(2.26) = -22.2 BUT WHAT ABOUT u ? 16 m/s horizontal speed = sqrt (22.2^2+16)^2 tan angle below horizontal = 16/22.2

*February 7, 2016*

**math**

n * (n-1) = 90 the rest cancels agree n^2 - n = 90 n^2 - n - 90 = 0 agree n = 10 or n = -9 agree 10 * 9 [ (n-2)! / (n-2)! ] = 90 for me all right

*February 7, 2016*

**math**

2 W + 2 (2 W + 3) = 66 6 W + 6 = 66 6 W = 60 etc

*February 7, 2016*

**algebra**

term 2 = a r term 4 = a r^3 term 5 = a r^4 term 1 = 1 term 3 = a r^2 ---------------------- ar (ar^3) = 2 (a r^4) a^2 r^4 = 2 a r^4 2 a = a^2 a^2 - 2 a = 0 a = 0 (won't work) or a = 2 now we need r I assume you mean the sum of the first 4 is 80 a + ar + ar^2 + a r^3 = 80 1...

*February 7, 2016*

**Maths, Problem solving**

x + x/4 +(x-90) = 180 2.25 x = 270 x = 120

*February 7, 2016*

**Statistic**

.75 and .83 .83 - .75 = .08 .08/.05 = 1.6 = z assuming your .05 is sigma and distribution normal http://davidmlane.com/hyperstat/z_table.html I get probability of .08 or above is about .05 I think the extra schooling helped

*February 7, 2016*

**physics**

That is really impossible to calculate. There is a change of momentum during the collision and force = change of momentum / duration of actual collision. That would be a fraction of a second but how long depends on the crushing characteristics of the body.

*February 7, 2016*

**maths**

90/90 - 28/90 = 62/90 = 31/45

*February 7, 2016*

**physics (mechanics)**

a = (20-15)/10 = 0.5 m/s^2 F = m a F = 1000 (0.5) + 270 F = 500 + 270 F = 770 N

*February 7, 2016*

**math**

combined speed = 110 110 mi/h * t = 660 t = 6 yes

*February 6, 2016*

**Math**

d = 4 q 10 d + 25 q = 390 10 (4q) + 25 q = 390 65 q = 390 q = 6 etc Your error is here: 0.40q+0.25q=3.90 then you said 65q=3.90 no 0.65 g = 3.90 3.90/0.65 = 6 not .06

*February 6, 2016*

**pysics**

Q = C m (T2-T1) = 400 (.5 kg) (116-16) note difference in deg K is the same as difference in deg C = 20,000 Joules

*February 6, 2016*

**Math**

34.375 / .125 = 275 I divided I do it the science way, multiply so units cancel you can do it by ratios .125 in/1 ft = 34.375 in / x ft .125 x = 34.375 x = 34.375 / .125

*February 6, 2016*

**Math**

34.375 in (1 ft/.125 in) = 275 ft

*February 6, 2016*

**Math**

That name game is just part of trying to hopelessly confuse me.

*February 6, 2016*

**Math**

LOL, talk about trying to confuse me ! If those are corresponding sides in two triangles and A is 4 times X then B is 4 times Y and m = 10/4 = 2.5 and C is 4 times Z and n = 16/4 = 4

*February 6, 2016*

**Math**

not without knowing the angles

*February 6, 2016*

**Physics 30**

Hey, just use Coulomb's Law F = k Q1 Q2 / d^2 if like charges, repel if opposite signs, attract see: http://en.wikipedia.org/wiki/Coulomb's_law

*February 6, 2016*

**physics & math**

sqrt ( 2*1.6*10) = 4 sqrt 2 = 5.66 m/s

*February 6, 2016*

**typos**

You mean g = - 32 ft/s^2 so h = Hi + Vi t + (1/2)a t^2 h = 105 - 9 t - 16 t^2 at ground: 0 = 105 - 9 t - 16 t^2 or 16 t^2 + 9 t - 105 = 0 t = [ -9 +/- sqrt(81+6720)]/32 t = [-9 +/- 82.5 ]/32 use positive time 2.30 seconds

*February 5, 2016*

**Physics**

V= i R 2 = .1 R and 2 = 5 R

*February 4, 2016*

**Physics help**

well electrostatic force causes hair to stand on end and gravity keeps the planets in orbit by the way

*February 4, 2016*

**Physics PLEASE PLEASE HELP! CONFUSED**

do vertical and horizontal problems separately Vertical Just plain fall, no initial velocity up or down so a) 10 = (1/2)(9.81) t^2 b) use that t to find out how far away he landed d = u t = 1.2 t c) vertical v = g t = 9.81 t horizontal u = 1.2 speed = sqrt (u^2+v^2) direction ...

*February 3, 2016*

**physics**

again that d is the part in the heavy liquid for the water depth use L-d

*February 3, 2016*

**physics**

B) rhoL L^2 d + rhoW L^2 (L-d) = rhoB L^3

*February 3, 2016*

**physics**

Force up on block = rhoL *L * L * d * g where d is the draft or distance submerged that has to equal the weight of the block which is rhoB L^3 g so rhoB L^3 g = rhoL L^2 d g d = (rhoB/rhoL) L d/L = rhoB/rhoL but we want (L-d)/L which is 1 - d/L 1 - d/L = fraction above = 1-...

*February 3, 2016*

**True & False explanations Physics**

When a projectile is fired at 45 deg. angle and is in free fall, the only point along the path that the acceleration of the object is zero is the instant when the object is at the highest point of its path. Answer: False Can someone explain how? ============================== ...

*February 3, 2016*

**physics**

v = Vi - g t v = 20 - 9.81(2) h = Vi t - 4.9 t^2 h = 20(2) - 4.9 (4)

*February 3, 2016*

**One Last Queston**

My vote is for A Nothing slows it down

*February 2, 2016*

**differential equations**

for purposes of integration n k m are constant then ds/dt = -ks (s^2/nm - S/n -s/m +1) = -k [ s^3/nm - s^2/n - s^2/m + s] =k[ -s^4/4nm +s^3/3n + s^3/3m -s^2/2 + c] You can play with this perhaps http://www.wolframalpha.com/input/?lk=3&i=plot++-s^4%2F4n+%2Bs^3%2F3n+%2B+s^3%2F3...

*February 2, 2016*

**Physics**

so weight = 4.11*9.81 = 40.3 N down Tension = 23.5 N up 23.5 - 40.3 = 4.11 a a = - 4.09 m/s^2 so a is down, weight wins

*February 2, 2016*

**but what about the weight?**

weight = m g = 4.11 * 9.81 Newtons

*February 2, 2016*

**Math**

V = pi r^2 h

*February 2, 2016*

**maths**

5/35 = x/21 x = 21 * 5 / 35

*February 2, 2016*

**Algebra**

I think you have typos but perhaps .75 x = 30

*February 2, 2016*

**Algebra**

in pennies: 4500 + 29.5 m = 9000 + 7 m 22.5 m = 4500 m = 200 miles

*February 2, 2016*

**math**

approximately 40828.19332

*February 2, 2016*

**Math**

56 * 4 = 224

*February 2, 2016*

**US History**

LOL - that was a media generated war ! It was the very origin of the term: "yellow journalism" starting with the explosion of the Battle ship Maine which seems to have been an engineering error but the press blamed on the Spanish. See: http://history.state.gov/...

*February 2, 2016*

**Which war ?**

Civil war? Vietnam ? Iraq?

*February 2, 2016*

**algebra**

100 a + 75 s = 14000 pennies a+s = 150 so a = 150-s 100(150 - s) + 75 s = 14000 15000 - 25 s = 14000 1000 = 25 s s = 40 then a = 150 - 40 = 110

*February 2, 2016*

**algebra**

2 x + 3 y = 252 4 x + 1 y = 244 multiply second equation by 3 2 x + 3 y = 252 12x + 3 y = 732 -----------------subtract - 10 x = - 480 x = 48 then y = 244-192 = 52

*February 2, 2016*

**algebra**

number = 10 x + y x+y = 12 y = 2 x so x + 2 x = 12 x = 4 then y = 8 so 48

*February 2, 2016*

**algebra**

f+4 = 3 (s+4) f-6 = 7(s-6)

*February 2, 2016*

**math Chem formula wrong**

3 % C 10 % Ca 87 % O Like no way CaCO3 40 + 12 + 48 = 100 molar mass 40% Ca, 12% C , 48% O so the real answer is 400 g , 120 g 480 g BUT using your strange numbers: in 100 grams: .03 * 100 = 3 g .1 * 100 = 10 g .87 * 100 = 87 g

*February 2, 2016*

**Math**

That is high precision. For low I would pick 3*10^3

*February 1, 2016*

**Science**

I guess they stick together. 8*10 - 6*50 = (6+8) v -220 = 14 v v = -15.7 m/s

*February 1, 2016*

**Math**

F = k x 10 = k (.5) k = 20 lb/in 15 = 20 x x = 0.75 in

*January 31, 2016*

**mathematics**

(6^5 /6^3) + 7^0 ??? 6^2 + 1 37

*January 31, 2016*

**science**

50 v = .1(50) v = .1 m/s

*January 31, 2016*

**Science**

Those are VECTORS You need BOTH magnitude and direction to add them. The resultant could have any magnitude between 20 and 70 meters

*January 31, 2016*

**Science**

r and Re F = G Mm/r^2 = (.25) G Mm/Re^2 or .25/Re^2 =1/r^2 .25 r^2 = Re^2 .5 r = Re r = 2 Re height = 2Re-Re = Re

*January 31, 2016*

**physics**

h = Hi + Vi t - 4.9 t^2 0 = 29 - 8.95 t - 4.9 t^2 t = [8.95+/-sqrt(8.95^2 + 4*29*4.9)]/(2*4.9) t = [8.95 +/-25.46 ] /9.81 use + t 3.51 seconds

*January 31, 2016*

**physics**

v = 19 - 9.81 t at top v = 0 t = 19/9.81 = 1.94 seconds to top at top h = 0 + 19 t - 4.9 t^2 h = 18.4 m high at top the same as the rise time 1.94 s the same 19 m/s but down now

*January 31, 2016*

**physics**

v = 0 = 81 - 5 t 800 = 81 t - 5.2 t^2 use that same stopping time t

*January 31, 2016*

**physics**

I guess we are to do this all in feet and seconds? v = 205 mi/h *5280ft/mi*(1h/3600s)) = 301 ft/s a = 301/2.7 = 111 ft/s^2 d = (1/2)(111)(2.7)^2 =406 ft

*January 31, 2016*

**Physics**

9.7*3 + 7.6*0 = 9.7 Va + 7.6 Vb so Va = (29.1 -7.6Vb)/9.7 then .5(9.7)(9)= .5(9.7)Va^2+.5(7.6)Vb^2

*January 31, 2016*

**Physics**

if acceleration is constant their average speed during the stop = 10/2 = 5 m/s 5 m/s * 30 s = 150 meters

*January 30, 2016*

**math**

21/x = 7/10 ? multiply both sides by 10 x 21 * (10 * x)/x = 7 * (10 * x)/10 210 = 7 x x = 210/7

*January 30, 2016*

**Science**

Yes, the answer is c

*January 30, 2016*

**Math**

2 y + 6 + 4 y =

*January 29, 2016*

**MATHS**

x + (5x-7) = 59 6x = 66 x = 11 and 5x - 7 = 55-7 = 48

*January 29, 2016*