# Posts by scott

Total # Posts: 2,157

**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

**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

**Chemistry**

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

**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

**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)]}

**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

**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

**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...

**Physics**

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

**Physics**

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

**Math**

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

**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

**science**

zero

**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

**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 ...

**math**

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

**Chem**

CaS ... calcium sulfide

**Chem**

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

**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

**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

**statistics**

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

**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

**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 ...

**math**

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

**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

**Chemistry**

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

**Chemistry**

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

**math**

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

**maths**

1/2 of 1/6 is 1/12

**pre cal**

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

**Algebra 2**

it would be infinite

**@ 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

**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 ...

**someone please help me. - Precalc**

tan(90º - Θ) = cotan(Θ) cotan(Θ) = cos(Θ) / sin(Θ) [cos(Θ) / sin(Θ)] * sin(Θ) = cos(Θ)

**Math**

x (.20) + (300 - x)(.40) = 300 (.28) .2 x + 120 - .4 x = 84

**physics**

the rock reaches its peak after 12/g s it ascends at an average rate of ... (12 m/s + 0 m/s) / 2 it then free falls from h m g h = ½ m v² ... v = √(2 g h) t = 2 h / v

**Physics**

a * [1 - (p / density of Hg)]

**algebra**

(s + 7)² = s² + 189 s² + 14 s + 49 = s² + 189 14 s = 140

**maths**

h(x) = 2 - x g(x) = x²

**maths**

f(x) = g[h(x)] g(x) = x³ h(x) = 2x + 1

**Physics**

the energy stored in the spring is ... ½ k x² ... this energy is K.E. when the spring is in the neutral position (the middle of its travel) K.E. = ½ m v² ... so the velocity and the amplitude are directly related to each other (both squared) a) velocity...

**Math**

a) h / 300 = tan(16º) ... h = 300 * tan(16º) b) tan(Θ) = h / (300 - 75)

**geometry**

the 3rd side must be greater than the difference, and less than the sum, of the 1st two sides

**Math**

[(8 * 60) + 37] * 25 ft

**physics**

the average velocity is ... 36 m / 2 s = 18 m/s gravity has slowed decelerated) the arrow by ... 9.8 m/s² * 2 s = 19.6 m/s [v + (v - 19.6)] / 2 = 18 ... v = 27.8 m/s (launch velocity) time to peak is ... 27.8 m/s / 9.8 m/s² peak height is ... time to peak * 27.8 / 2 ...

**Geometry**

after translation ... [(-6 + 3),(-4 + 5)] = (-3,1) after rotation ... (1,3)

**Maths**

B = 3 J ... J = B/3 B = J + 450 ... B = B/3 + 450 ... 2B/3 = 450 ... B = 450 * 3/2

**Statistics**

15 is 1.5 above the mean ... this is 1.5/7.3 standard deviations ... .2055 use a z-score table to determine the fraction of the population this represents 15 yr or less ... 58%

**engineering mechanics**

normal ... m g cos(30º) parallel ... m g sin(30º)

**math**

1/A + 1/B = 1/8 ... 15/B = 15/8 - 15/A 6/A + 15/B = 1 ... 6/A - 15/A + 15/8 = 8/8 ... -9/A = -7/8 ... -72 = -7A

**Math**

x (25 - 2x) (32 - 2x) = 1575 expand the cubic equation find a solver online (use google)

**physics**

10 min = 600 s 600 s (20 m/s + 30 m/s) = 30 km ave spd = 30 km / 20 min = 1.5 km/min 10 km / 20 m/s = 500 s 10 km / 30 m/s = 1000/3 s 20 km / (1500/3 s + 1000/3 s) = ... 60 / 2500 km/s = 36/25 km/min = ... 1.44 km/min

**CHECK MY ALGEBRA 2**

?????

**CHECK MY ALGEBRA 2**

a hole is a disruption at a single point ... try [(x - 4) / (x - 4)] ... the division by zero causes the discontinuity, but the equal numerator means no other point is affected f(x) = (x - 4) / [(x - 4) (x + 2)]

**Physics**

assumptions ... the person does not ride the ice down ... the height of the break is even with the top of the slope the gravitational potential energy of the ice is converted to kinetic energy and then heat by friction the total energy dissipated is ... m g h = 100 kg * g * ...

**College physics**

this is the Doppler effect (google it) the pitch (frequency) is higher because you are moving toward the source f = [343 / (343 - 5)] * 4000

**Physics**

Vh = 3 m/s² * 30 s = 90 m/s ½ m Vv² = m g h ... Vv = √(2 g h) = √( 2 * 10 * 80) tan(Θ) = Vv / Vh

**chemistry**

pH = 14 - pOH pOH = - log[OH⁻] = - -8 = 8

**Math**

top area???

**PHYSICS**

acceleration ... d = 30 s * [(20 m/s + 0 m/s) / 2] cruise ... d = 15 s * 20 m/s deceleration ... d = 5 s * [(20 m/s + 0 m/s) / 2] add the three distances

**math: permutations**

couple in 1st row ... 2 ways for 1st row ... 4! ways for 2nd row couple in 2nd row ... 4*5 ways for 1st row ... 4! ways for 2nd row [(4 * 5) + 2] * 4!

**math:age**

2 s = u 3 (s - 9) = u 3 s - 27 = 2 s

**Help me anyone - Pre-Calc**

Θ is in radians 20º = (2 π / 18) rad 2340 = ½ (2 π / 18) r² 18 * 2340 / π = r²

**math**

e = p + 50 time = distance / rate ... 1.6 (1800 / e) = 1800 / p substituting ... 1.6 [1800 / (p + 50)] = 1800 / p solve for p, then substitute back to find e and the times

**Calculus - Differentials**

the error (in D) is ±.05 A = π D² dA = 2 π D dD = .6 π same difference...

**Calculus**

h = height up wall d = distance from wall by Pythagoras... h² + d² = 20² differentiating ... 2 h dh/dt + 2 d dd/dt = 0 substituting ... (2 * h * -3) + (2 * d * 4) = 0 ... 8 d = 6 h ... d = ¾ h h² + (¾ h)² = 400 solve for h substitute back...

**physics**

[16 * cos(20º)] / 4.9 the values in the problem are to 2 significant figures ... not sure about hundredths accuracy

**Science**

I can be traced back to 3000bc, often go unnoticed, can be overhead, under feet or somewhere in between, evolution has changed me, am lighter than I used to be, and can protect your investment.

**Physics**

distance = 70 * 5 = 350 km speed = distance / time = 350 / (5 + 2)

**Math**

3, 5, 9, 15

**Physics**

N is to the left google "right hand SOLENOID rule"

**chemistry**

(3 / 2) * 41.0

**Math**

if r = -2, then the denominator is zero...a big no-no factor the numerator and go with B

**Chemistry**

1.63 is [SO₂]² ... take the square root

**Physics**

heat capacity is proportional to mass mass is proportional to volume volume is proportional to the cube of the radius heat cap. ratio is ... 1³:2³

**Physics**

(a) 2400 + 1800 (b) 1800 / (2400 + 1800)

**math**

h = 4 mi * tan(5º) = 4 * 5280 ft * tan(5º)

**Math**

the area of the real world room is (36 / 2.5)² times the area of the plan

**Physics**

the velocity is half, so the remaining energy (kinetic) is a quarter of the original 3/4 of the energy to penetrate 15 cm it will penetrate another 5 cm

**Science**

m g h = ½ m v² h = v² / (2 g) h = ½ g t² ... v² / (2 g) = ½ g t² t = v / g .. this is ½ the flight time

**Math**

6000 = 2500 (1 + r/4)^(10 * 4) 2.4 = (1 + r/4)^40 log(2.4) = 40 log(1 + r/4) .0095053 = log(1 + r/4) 1.002213 = 1 + r/4

**physics**

the expansion coefficient is ... α = 1.20E-5 m /m·ºK ΔL = 1.20E-5 * 12.5 * (154 - 5) L = 12.500 + ΔL

**Physics**

energy (work) = 1/2 k x^2 w = 1/2 * 950 N/m * (.06 m)^2

**Math**

multiplying by 1/3 ... (1/x) / [x^(-2/3)] = 1 / [x^(1/3)] multiplying by x^(-2/3) ... 1/x = [x^(-2/3)] / [x^(1/3)] ... = 1 / [x^(3/3)] = 1/x

**physics**

units conversion a = v / t d = Vave / t = 30 mph / 3.2 s

**Physics**

average velocity is ... (.36 + 0) / 2 t = d / v = .8 m / .18 m/s acceleration ... a = .36 m/s / t f = 80 kg * a

**Math**

f - s = 28 2.5 (f + s) = 2320 f + s = 928 adding equations to eliminate s ... 2 f = 956

**chemistry**

He⁺ because the greater charge of the nucleus keeps a "tighter" hold on the electron

**physic**

you need the coefficient of friction to solve this

**physic**

g = 32.2 ft/s (a) 3.73 * 32.2 = w (lbs) (b) 3.73 * (32.2 + 5.5) = w (c) same as (a) (d) 3.73 * (32.2 - 5.5) = w

**General Physics**

integration is the correct approach work (energy) = F(x) dx the force goes to zero at √2.6, and then goes negative ... this is also the point of max energy

**Algebra 2**

they appear to be the same line (colinear)

**math 101**

145 is one s.d. above the mean 68% of scores are in this range 34% are above the mean 50% of scores are below the mean that leaves 16% of scores above 145

**maths**

good solution, Steve

**maths**

actually, slope-intercept is better

**maths**

find the equations (point-slope) of the diagonals and set them equal

**math ratios**

1 + 6 = 7 7 k = 21 ... k = 3 3 water and 18 fertiliser

**Physics**

m g h = .12 J .012 * 9.8 * h = .12

**physics**

the average speed is 40 m/s so it takes 25 s to cover the km the acceleration is 3.2 m/s² ... 80 m/s / 25 s speed halfway 500 = ½ * 3.2 * t² ... find t and multiply by the acceleration to find the speed half speed 40 m/s / 3.2 m/s² = 12.5 s ...average ...

**Math**

the Richter scale is logarithmic 10^(8.8 - 5.3)