Saturday
July 30, 2016

Posts by Scott

Total # Posts: 1,137

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

someone please help me. - Precalc
tan(90º - Θ) = cotan(Θ) cotan(Θ) = cos(Θ) / sin(Θ) [cos(Θ) / sin(Θ)] * sin(Θ) = cos(Θ)
July 27, 2016

Math
x (.20) + (300 - x)(.40) = 300 (.28) .2 x + 120 - .4 x = 84
July 27, 2016

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
July 27, 2016

Physics
a * [1 - (p / density of Hg)]
July 27, 2016

algebra
(s + 7)² = s² + 189 s² + 14 s + 49 = s² + 189 14 s = 140
July 27, 2016

maths
h(x) = 2 - x g(x) = x²
July 27, 2016

maths
f(x) = g[h(x)] g(x) = x³ h(x) = 2x + 1
July 27, 2016

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...
July 27, 2016

Math
a) h / 300 = tan(16º) ... h = 300 * tan(16º) b) tan(Θ) = h / (300 - 75)
July 27, 2016

geometry
the 3rd side must be greater than the difference, and less than the sum, of the 1st two sides
July 26, 2016

Math
[(8 * 60) + 37] * 25 ft
July 26, 2016

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 ...
July 26, 2016

Geometry
after translation ... [(-6 + 3),(-4 + 5)] = (-3,1) after rotation ... (1,3)
July 26, 2016

Maths
B = 3 J ... J = B/3 B = J + 450 ... B = B/3 + 450 ... 2B/3 = 450 ... B = 450 * 3/2
July 26, 2016

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%
July 26, 2016

engineering mechanics
normal ... m g cos(30º) parallel ... m g sin(30º)
July 26, 2016

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
July 26, 2016

Math
x (25 - 2x) (32 - 2x) = 1575 expand the cubic equation find a solver online (use google)
July 25, 2016

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
July 25, 2016

CHECK MY ALGEBRA 2
?????
July 25, 2016

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)]
July 25, 2016

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 * ...
July 25, 2016

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
July 25, 2016

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
July 25, 2016

chemistry
pH = 14 - pOH pOH = - log[OH⁻] = - -8 = 8
July 24, 2016

Math
top area???
July 24, 2016

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
July 24, 2016

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!
July 24, 2016

math:age
2 s = u 3 (s - 9) = u 3 s - 27 = 2 s
July 23, 2016

Help me anyone - Pre-Calc
Θ is in radians 20º = (2 π / 18) rad 2340 = ½ (2 π / 18) r² 18 * 2340 / π = r²
July 23, 2016

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
July 23, 2016

Calculus - Differentials
the error (in D) is ±.05 A = π D² dA = 2 π D dD = .6 π same difference...
July 23, 2016

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...
July 23, 2016

physics
[16 * cos(20º)] / 4.9 the values in the problem are to 2 significant figures ... not sure about hundredths accuracy
July 21, 2016

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.
July 21, 2016

Physics
distance = 70 * 5 = 350 km speed = distance / time = 350 / (5 + 2)
July 21, 2016

Math
3, 5, 9, 15
July 20, 2016

Physics
N is to the left google "right hand SOLENOID rule"
July 20, 2016

chemistry
(3 / 2) * 41.0
July 20, 2016

Math
if r = -2, then the denominator is zero...a big no-no factor the numerator and go with B
July 20, 2016

Chemistry
1.63 is [SO₂]² ... take the square root
July 20, 2016

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
July 20, 2016

Physics
(a) 2400 + 1800 (b) 1800 / (2400 + 1800)
July 20, 2016

math
h = 4 mi * tan(5º) = 4 * 5280 ft * tan(5º)
July 19, 2016

Math
the area of the real world room is (36 / 2.5)² times the area of the plan
July 19, 2016

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
July 19, 2016

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
July 19, 2016

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
July 19, 2016

physics
the expansion coefficient is ... α = 1.20E-5 m /m·ºK ΔL = 1.20E-5 * 12.5 * (154 - 5) L = 12.500 + ΔL
July 18, 2016

Physics
energy (work) = 1/2 k x^2 w = 1/2 * 950 N/m * (.06 m)^2
July 18, 2016

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
July 18, 2016

physics
units conversion a = v / t d = Vave / t = 30 mph / 3.2 s
July 18, 2016

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
July 18, 2016

Math
f - s = 28 2.5 (f + s) = 2320 f + s = 928 adding equations to eliminate s ... 2 f = 956
July 17, 2016

chemistry
He⁺ because the greater charge of the nucleus keeps a "tighter" hold on the electron
July 16, 2016

physic
you need the coefficient of friction to solve this
July 16, 2016

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
July 16, 2016

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
July 15, 2016

Algebra 2
they appear to be the same line (colinear)
July 15, 2016

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
July 15, 2016

maths
good solution, Steve
July 15, 2016

maths
actually, slope-intercept is better
July 15, 2016

maths
find the equations (point-slope) of the diagonals and set them equal
July 15, 2016

math ratios
1 + 6 = 7 7 k = 21 ... k = 3 3 water and 18 fertiliser
July 15, 2016

Physics
m g h = .12 J .012 * 9.8 * h = .12
July 14, 2016

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 ...
July 14, 2016

Math
the Richter scale is logarithmic 10^(8.8 - 5.3)
July 14, 2016

physics
it takes the 1st stone 2 s to reach its peak and return to the top of the tower, now going downward with the same velocity as the 2nd stone that velocity is 9.8 m/s when it reaches the ground, its velocity is 39.2 m/s...4 s * 9.8 m/s its average velocity is 24.5 m/s ... (9.8...
July 14, 2016

science
.001 moles / .5 L = .002 M
July 14, 2016

science
λ =330 m/s / 1E4 cycles/s = 33 mm
July 14, 2016

physics
the average speed is 10.0 m/s ... 70.0 m / 7.00 s 1st point speed is 5.00 m/s ... 10 = (15 + 5) / 2 acceleration is (10.0 m/s / 7.00 s)
July 13, 2016

Science
mass * [heat of vaporization + (specific heat * temp change)]
July 13, 2016

Chemistry
a mole of ANY gas occupies 22.4 L at stp (5.2 / 22.4) * Avogadro's number
July 13, 2016

Algebra
(3 / 2s) + (1 / s) = 1 / 9 27/2 + 9 = s = 45/2 b = 2/3 s = 15
July 13, 2016

physics
combined force is 2 kN each pier acts as a fulcrum in a class 2 lever system 6 m * 2 kn = 10 m * f1 4 m * 2 kn = 10 m * f2
July 12, 2016

math
f + s = 205 5 f + 15 s = 2025 ... f + 3 s = 405 subtracting equations ... 2 s = 200
July 11, 2016

Physics
1 / R + 1 / 400 = 5 / R 1 / 400 = 4 / R
July 11, 2016

Chemistry
a liter of solution has a mass of 1.114 kg 20.0% of that is H₃PO₄ ... 222.8 g the molar mass of H₃PO₄ is ... 97.99 g so the moles/L is ... 222.8 / 97.99 the 20.0 means 3 sig fig
July 11, 2016

Math
g(x) = -2 (2x - 4)³ - 1
July 11, 2016

Math
f(x) = (x + a) (x + b)² (x + c)³
July 11, 2016

maths
2 sin(21º) = cos(69º) sin(29º) = cos(61º) so it's twice sin² + cos²
July 11, 2016

math,maths
x/x + 2/x ≥ .2 1 + 2/x ≥ .2 2/x ≥ -.8 2 ≥ -.8 x -5/2 ≤ x
July 10, 2016

Math
the distance is the same 10 (s - 21) = 7 s 10 s - 210 = 7s
July 10, 2016

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