Thursday

February 23, 2017
Total # Posts: 1,821

**Chemistry**

so the concentration of H⁺ from the HCl is ... 1 mole in 6 moles of water pH is based on moles of H⁺ per liter of solution water's volume is 18 mL per mole (based on the molar mass) so 6 moles is 108 mL so, [H⁺] = 1 mole / .108 L pH is the negative log of...

*August 27, 2016*

**Physics I - Modern**

the momentum is the product (multiply) of the relativistic mass and the velocity the relativistic mass is the rest mass multiplied by gamma (the relativistic "fudge factor") gamma = 1 / sqrt[1 - (v² / c²)] p = gamma * rest mass * v hyperphysics (web) is a ...

*August 25, 2016*

**math**

that is the number for all correct (or incorrect) see the answer to your other posted question

*August 24, 2016*

**math**

(a) it is a normal distribution (bell curve)n with the most likely score being half right (or wrong) you could plot the points using your binomial distribution from part (b) (b) the exponents in an individual term should sum to 15 only your last term does that otherwise, looks...

*August 24, 2016*

**Chemistry**

H₃BO₃ is triprotic (3 H⁺ per molecule) 29.15 * .025 = M * 3 * 25.0

*August 23, 2016*

**Algebra**

x (7 - 2x) (12 - 2x) = 33 4x³ - 38x² + 84x - 33 = 0 (9 - √15) / 2

*August 23, 2016*

**Physical science check my answers**

4. traveling a greater distance in the same amount of time means you went faster/slower?

*August 23, 2016*

**Chemistry**

a dm^3 is a liter two chloride ions per calcium chloride molecule .04 * .45 * 2

*August 22, 2016*

**solid mensuration**

π r² = 452 ... r = 12 the triangle formed by the chord and the radii from the ends has a central angle of 120º so 2/3 of the circle (240º / 360º), plus the area of the triangle; is the area of the larger segment

*August 21, 2016*

**Physics**

A. 239 = ½ * 3.7 * t² B. v = a t = -3.7 * t ... t is from part A

*August 21, 2016*

**Physics**

A. t = 50 ft/s / 32.2 ft/s² B. the velocity is zero at the peak ... so the average ascending velocity is 25 ft/s ... the displacement is 25 ft/s multiplied by the time from part A C. the time is half of the time from part A ... the average velocity is (50 + 25)/2 ft/s...

*August 21, 2016*

**Algebra**

you are correct (-11)^2 would be 121

*August 21, 2016*

**Math**

W = H + 4 L = W + 8 = H + 4 + 8 = H + 12 A = 2H (W + L) = 2 H (2H + 16) 512 = 4 H² + 32 H 128 = H² + 8 H 0 = H² + 8 H - 128 solve for H, then substitute back to find W and L

*August 21, 2016*

**trigonometry**

11π / 12 corresponds to a 15º reference angle in Q II 15º is half of 30º use a half-angle identity to find the exact value

*August 20, 2016*

**Physics**

the man is twice as far from the fulcrum as the rock so the effort is half the weight of the rock

*August 20, 2016*

**PHYSICS topic is pressure**

it is the lowered PARTIAL PRESSURE of oxygen, coupled with the increased PP of carbon dioxide that causes problems

*August 20, 2016*

**PHYSICS topic is pressure**

a deep well allows for little air circulation and the components of the atmosphere can stratify to a certain extent oxygen (which we need to breathe) is not the densest component the noble (inert) gas, argon, makes up about 1% of air; and is the heaviest as already mentioned, ...

*August 20, 2016*

**SCIENCE**

see the physics question 3 above yours

*August 20, 2016*

**Maths Algebra**

b = g + 334 b + g = 572 substituting ... g + 334 + g = 572

*August 20, 2016*

**Trig**

a sine value of .5 means a 30º reference angle in Q III, the angle is ... 180º + 30º = x

*August 20, 2016*

**Maths Algebra**

3/5 = 24/40 1/4 = 10/40 1/8 = 5/40 1/40 is left for foot travel 1/40 j = 2 km ... j = 80 km

*August 19, 2016*

**Maths Algebra**

9 is 1/4 of 1/2 of the herd 1/8 h = 9

*August 19, 2016*

**Math**

46 divided by 1

*August 17, 2016*

**Physics**

the kinetic energy of the ball at launch equals the gravitational potential energy at the peak ½ m v² = m g h v = √(2 g h) = √(2 * 9.8 * 20) m/s

*August 17, 2016*

**Trigo**

the length of belt that passes over the pulleys is the same 18 * 2π * 6 = 5 * 2π * r

*August 17, 2016*

**Math**

the force is proportional to the area 30 N / 50 cm² = f / 1500 cm²

*August 16, 2016*

**mathematics**

30000 = x [1 + (.12/12)]^(5 * 12) 32500 = y [1 + (.12/12)]^(7 * 12) 36000 = z [1 + (.12/12)]^(10 * 12) find x, y, and z and add them together log(3000) = log(x) + 60 log(1.01) log(3000) - [60 log(1.01)] = log(x) 10^[log(x)] = x

*August 16, 2016*

**maths**

12 is the common denominator for 6, 3, and 4 10/12 - 8/12 + 15/12 = 17/12 = 1 5/12

*August 16, 2016*

**Math**

3/5 men...so 2/5 women the difference (1/5) equals 12 5 * 12 = ?

*August 16, 2016*

**Maths**

torque = force * distance 200 Nm = f * .40 m

*August 16, 2016*

**PreCalc**

you want the sin⁻¹ function on your calculator sin⁻¹(0.65) = Θ = .7076 , 2.4340

*August 15, 2016*

**Math**

8+{4 x [(2+7) / 3]} = 20

*August 15, 2016*

**PHYSICS/SCIENCE**

a third as much as 15.0 g

*August 13, 2016*

**Math**

x² + 7x + 12 = 0 (x + 3) (x + 4) = 0 x = -3 , x = -4

*August 13, 2016*

**Physics/Science**

150 cal to take the water to 0º C 79.7 cal/g to freeze it

*August 13, 2016*

**Math**

c = 3.5 x + 10

*August 12, 2016*

**Math-Direct Variation**

x = k y 3 = k * 6 ... k = 1/2 x = 1/2 * 2/3 = 1/3

*August 12, 2016*

**probability statistics**

between means ... 4000 < n < 7000 3 choices for the 1st digit ... 4, 5, 6 8 for the 2nd digit 7 for the 3rd digit 6 for the 4th digit numbers = 3 * 8 * 7 * 6

*August 12, 2016*

**statistics**

there are 11 letters 3 of them occur twice possible arrangements equal ... 11! / (2! * 2! * 2!)

*August 12, 2016*

**Calculus**

velocity is dx/dt integrating gives position t/42 = dx/dt t/42 dt = dx integrating ... t²/84 = x = 100/21

*August 10, 2016*

**math**

there are 9C4 ways of selecting four printers there are 5C4 ways of selecting four good printers the probability is ... 5C4 / 9C4

*August 10, 2016*

**Science**

the simplified range equation is ... Rmax = v² / g ... 100 = v² / g ... 100 g = v² when an object is thrown straight up, the initial kinetic energy becomes gravitational potential energy ... ½ m v² = m g h ... v² / (2 g) = h combining the two ...

*August 8, 2016*

**math**

b + c = 45 / 2.5 = 18 kph b - c = 39 / 3.25 = 12 kph adding equations (to eliminate c) ... 2 b = 30 kph solve for b substitute back to find c

*August 7, 2016*

**chemistry**

a mole contains Avogadro's number of particles 5 moles = 5 * 6.02E23

*August 7, 2016*

**Geometry**

90º - a = (180º - a) / 5 450 - 5a = 180 - a 270 = 4a

*August 7, 2016*

**Algebra/Quadratic Functions**

the minimum lies on the axis of symmetry x min = -b / 2a = -(-200) / 2*2 = 50

*August 7, 2016*

**Calc**

f(x) = x^2+(1000-x)^2 ... = x² + 1E6 - 2000x + x² ... = 2x² - 2000x + 1E6 the minimum is on the axis of symmetry at x=500 ... the function increases from there so as x increases (below x=500), the function decreases f(0) = 0² + (1000 - 0)² = 1000²...

*August 7, 2016*

**Math calculus**

s.a. = 6 s² da/dt = 12 s ds/dt v = s³ ... 8 = 2³

*August 7, 2016*

**Maths**

M = 2R M + 11 + R + 11 + 3 = 75 Roy's dessert ... 11 + 3 = $14 3R + 25 = 75 ... R = 50/3 Roy's meal ... $50/3

*August 7, 2016*

**Science**

f = 1500 * g * .2

*August 6, 2016*

**maths**

4 (1 / 2 μf) = 1 / Ce Ce = 2 μf / 4

*August 6, 2016*

**Math**

d = h cot(32º) d - 8 = h cot(43º) 8 = h [cot(32º) - cot(43º)] h = 8 / [cot(32º) - cot(43º)]

*August 6, 2016*

**Math**

3/5 = 6/10 ... so there were 6 groups of boys the 2/5 of the class that were girls resulted in 2 groups of 1/5 each an aside ... the girls' groups were twice as large as the boys' groups

*August 5, 2016*

**physics**

don't know if significant figures are an issue but there are two in the data, and four in the result

*August 5, 2016*

**Science**

the horizontal velocity is the total velocity multiplied by cos(30º) at the topmost point, there is no vertical velocity ... so the K.E. is ... E cos²(30º)

*August 4, 2016*

**Algebra**

nancy starts with $50 more, but annie can save $5 more per week 50 / 5 = 10 weeks

*August 4, 2016*

**physics**

h = ½ g t² + 30 t = -4.9 t² + 30 t substitute 20 for h to find the time ... use the quadratic formula the time of max h is on the axis of symmetry of the parabola ... t = -b / 2a = -30 / -9.8 ... plug in the time to find h max the velocity is zero at max h the...

*August 4, 2016*

**physics**

average velocity = distance / time = 42 m / 2 s = 21 m/s average velocity = (initial + current) / 2 gravity slowed the arrow for 2 sec ... current = initial - (2 * 9.8) (Vi + Vi - 19.6) / 2 = 21 m/s solve for Vi time up = time down flight time = 2 (Vi / g)

*August 4, 2016*

**Math**

5 pies means 20 quarters (5*4) 3 quarters per neighbor means 6 neighbors, with two quarters left over 3*6 = 18 ... 18 + 2 = 20

*August 4, 2016*

**I need help - precalc**

1/√3 is the tangent of 30º or π/6 ... this is the reference angle -1/√3 is the tangent of the reference angle in quadrants II and IV so the x-values are ... 5π/6, 11π/6, and 17π/6

*August 4, 2016*

**Math**

no it is three decimal places to the right, so it is one thousandth the value of the 1st five (10^-3)

*August 4, 2016*

**math**

you could say "a" percent is like "a" peanut...one it doesn't use the term "percentage" regardless, the question is not well worded (1.01 n) * .20 = 400

*August 4, 2016*

**biology**

the high specific heat will help keep the pond from becoming a "fish stew"

*August 4, 2016*

**Biochemistry**

pOH = 14 - pH = 2.5 [OH⁻] = 1.0E-2.5 = .0032 M 1.75 * .0032 = .0056 moles of KOH multiply by the molar mass to find the quantity required

*August 3, 2016*

**chemistry**

.250 L of a .1 M solution contains .025 moles of solute mass needed is ... .025 * 204.23 g

*August 3, 2016*

**Chemistry**

in general; the lower the elevation, the higher the atmospheric pressure but the pressure (barometric) varies with weather conditions B might be the best answer for this somewhat ambiguous question

*August 3, 2016*

**math order of operations**

PEMDAS parentheses, exponents, multiplication, division, addition, subtraction 2*2*3 = 12 12/12 = 1 10 - 1 = 9 9*7 = 63 10 + 63 = 73

*August 3, 2016*

**Chemistry**

volume is inversely related to pressure (Boyle's Law) P1*V1 = P2*V2 108 * 8 = 224 * V2

*August 3, 2016*

**math**

it's in two steps 700 is the start of the 1st step, 7.5% for 6 years ... the result becomes the start of the 2nd step, 8.25% for 4 years

*August 3, 2016*

**Physics**

the horizontal pulling force is ... 260 cos(30º) the vertical pulling force is ... 260 sin(30º) the coefficient of sliding friction is ... [260 cos(30º)] / ... {450 - [260 sin(30º)]}

*August 3, 2016*

**Math**

it could be a looong summer... there are an infinite number of solutions if n and m are the numbers ... n - m = 3¼ , or , n = m + 3¼ m can be ANY mixed number

*August 2, 2016*

**statistics**

2.15 is .85 below the mean this is .85/.5 s.d. (1.7) use a z-score table to find the fraction of the population in this range about .045

*August 2, 2016*

**I need help please - Pre-Calc**

1/√2 is the cosine of 45º (π/4) ... that is the reference angle -1/√2 is the cosine of ... ±3π/4 ... add or subtract multiples of 8π/4 to find the values on the interval x values...-13π/4, -11π/4, -5π/4, -3π/4, 3π...

*August 2, 2016*

**Physics**

a = f / m a = [108.1 - (10 * g)] / 10

*August 2, 2016*

**Physics**

f = m a f = 3 kg * (25 m/s / .10 s)

*August 2, 2016*

**Math**

4 - $2 1 - $5 1 - $10 1 - $50

*August 2, 2016*

**Chemistry**

the molar mass of silver chloride is 143.32 g the molar mass of silver is 107.87 g so the mass of silver in the processed sample is ... .2865 * 107.87 / 143.32 the processed mass divided by the original sample mass is the purity of the original sample

*August 2, 2016*

**science**

zero

*August 1, 2016*

**physics**

a boy uses a slingshot to launch a rock with a velocity of 30m/s how long does it take it to reach a height of 20m,what maximum height does the rock reach, what is the velocity of the rock at this height, what is the velocity of the rock just before it lands

*August 1, 2016*

**physics**

the required takeoff speed for a large airplane is 180mi/hr(80m/s)the plane is capable of accelerating at a rate of 4m/s^2 assume the plane starts at rest, determine the minimum runway length required for this plane to safely take off, a smaller airplane requires a takeoff ...

*August 1, 2016*

**math**

a. v = x (8 - 2x) (15 - 2x) b. x must be less than 4 (the point where the 2nd factor goes to zero)

*July 30, 2016*

**Chem**

CaS ... calcium sulfide

*July 30, 2016*

**Chem**

increasing the temperature (adding energy), will drive the reaction to the left

*July 30, 2016*

**math**

AC ... y = -2 x + 20 BD ... y = 1/2 x D (8,4) BD = √(64 + 16) AD = √(9 + 36) area ABD = ½ √(80 * 45) = 30 area ABEF = 10² = 100

*July 30, 2016*

**math**

a graphical solution seems the most straight forward B(0,0) C(10,0) E(10,10) A(5,10) F(0,10) find the equation for AC, and then the equation for BD D is the intersection of the lines calculate the lengths of BD and AD to find the area of ABD

*July 30, 2016*

**statistics**

the failure rate is 15% the probability of both bulbs being bad is ... .15 * .15

*July 29, 2016*

**Chemistry**

C₃H₈ + 5 O₂ --> 3 CO₂ + 4 H₂O 4 moles of C₃H₈ would normally produce 12 moles of CO₂ ... but there is insufficient O₂ the O₂ is 1/5 of what is necessary, so the yield will be ... 1/5 * 12 moles

*July 29, 2016*

**Science**

the Earth completes one revolution in 24 hr so, how long is the 40th parallel? the "rotational" radius is equal to the radius of the Earth times cos(40º) the length of the parallel (circumference) is 2π times the radius divide the circumference by 24 hr to ...

*July 29, 2016*

**math**

Steve is referring to the 5-12-13 Pythagorean triple

*July 28, 2016*

**math**

S * L = 60 S² + L² = (S + 8)² S² + (60 / S)² = (S + 8)² S² + (3600 / S²) = (S + 8)² S⁴ + 3600 = S⁴ + 16 S³ + 64 S² S³ + 4 S² - 225 = 0 S = 5

*July 28, 2016*

**Chemistry**

1.2E24 / 6.0E23 = 2.0 moles 4.0 moles are added

*July 28, 2016*

**Chemistry**

there are 6.0 x 1E23 molecules in a mole 2.0 moles + 4.0 moles

*July 28, 2016*

**math**

d / r = t 240 / (b + 20) = 180 / b 240 b = 180 b + 3600

*July 28, 2016*

**maths**

1/2 of 1/6 is 1/12

*July 27, 2016*

**pre cal**

the 5th order term is the driver it is an odd power, so the function will have the same sign as x

*July 27, 2016*

**Algebra 2**

it would be infinite

*July 27, 2016*

**@ Ms. Sue**

the key here is "modern" humans (like us) Isaiah is using 6 million in some population growth scenario and getting weird results he's not interested in the start of the genus homo, he want to count people

*July 27, 2016*

**Science**

"modern" humans (us) arrived on the scene about 30 - 50 thousand years ago around the end of the last ice age there was limited interbreeding with the Neanderthals -- who were on the way out there have NOT been people like us around for 6 million years plug a ...

*July 27, 2016*