# Posts by Scott

Total # Posts: 2,423

**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)

**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...

**science**

.001 moles / .5 L = .002 M

**science**

λ =330 m/s / 1E4 cycles/s = 33 mm

**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)

**Science**

mass * [heat of vaporization + (specific heat * temp change)]

**Chemistry**

a mole of ANY gas occupies 22.4 L at stp (5.2 / 22.4) * Avogadro's number

**Algebra**

(3 / 2s) + (1 / s) = 1 / 9 27/2 + 9 = s = 45/2 b = 2/3 s = 15

**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

**math**

f + s = 205 5 f + 15 s = 2025 ... f + 3 s = 405 subtracting equations ... 2 s = 200

**Physics**

1 / R + 1 / 400 = 5 / R 1 / 400 = 4 / R

**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

**Math**

g(x) = -2 (2x - 4)³ - 1

**Math**

f(x) = (x + a) (x + b)² (x + c)³

**maths**

2 sin(21º) = cos(69º) sin(29º) = cos(61º) so it's twice sin² + cos²

**math,maths**

x/x + 2/x ≥ .2 1 + 2/x ≥ .2 2/x ≥ -.8 2 ≥ -.8 x -5/2 ≤ x

**Math**

the distance is the same 10 (s - 21) = 7 s 10 s - 210 = 7s

**math**

r + b = 365 ... 10 r + 10 b = 3650 9.5 r + 10 b = 3645 subtracting equations ... .5 r = 5

**Pre-Calculus 11**

squaring ... 9 - 6x + x² = x² - 5 x = 7/3

**math**

L = w + 5 w * (w + 5) = 500 w² + 5 w - 500 = 0 factoring ... (w + 25) (w - 20) = 0 w = 20 ... L = 25

**Physics**

heat = mass * temperature change * specific heat for the water heat = 200 g * 7.2 ºC * 1 cal/gºC heat gained by the water is the heat lost by the metal for metal heat = 95 g * 70.8 ºC * s.h. s.h. = (water heat) / (95 * 70.8) be aware of significant figures in ...

**Algebra**

ln(y) + 5 ln(y+1)

**physics**

each of the four sides of the square is 5 Ω diagonally, there are two parallel paths of two 5 Ω resistances in series each path is 10 Ω (5 + 5), and the two paths in parallel results in a net resistance of 5 Ω

**physics**

a hanging spring with a freely hanging mass the force (from gravity) is ... m * g = .98 N k = F / d = .98 N / .01 m = 98 N/m

**PHYSICS**

multiplying or dividing ...add the percent uncertainties 16 ± 2.25% the cm are cancelled in the division process...it's just a ratio

**Algebra**

squaring both sides ... 36 = n^(2x) multiplying by n ... 36 n = n^(2x + 1)

**Algebra**

the drop time is ... t = 132 ft/s / 32 ft/s² it starts from rest, so the average velocity is ... (0 + 132) / 2 ft/s the distance is ... d = drop time * average velocity

**Science**

going directly from a solid to a gas is called sublimation

**Physics**

heat = mass * temp change * specific heat make sure the units are consistent

**Calculus**

the horizontal components of the two ropes' tensions balance each other the combined vertical components equal 400 N sin(60º) = T1v / 400 N T2v = 400 N - T1v cos(60º) = T1h = T2H T2 = √[(T2v)² + (T2h)²]

**Chemistry**

the iron is oxidized the hydrogen is reduced

**Physics**

80 C / .001 s = 80000 C/s = 80 kA

**Math (Quadratic Equations)**

(1 / A) + (1 / B) = 1 / 12 (1 / A) + [1 / (A - 7)] = 1 / 12 12 A - 84 + 12 A = A * (A - 7) 24 A - 84 = A² - 7 A 0 = A² - 31 A + 84 factor the quadratic to find A

**Math**

-3 is not a root the roots are ... -3±i 4, -3+i, -3-i