Friday

January 20, 2017
Total # Posts: 1,636

**Math**

volume of water is volume of pyramid minus the volume of pyramid above the water v = 480 - 480 (1 - d/10)² ...= 480 - 480 (1 - d/5 + d^2/100) ...= 96 d - 4.8 d^2 dv/dt = 96 dd/dt - 9.6 d dd/dt 2 = 96 dd/dt - 9.6 * 4 * dd/dt 2 = 96 dd/dt - 38.4 dd/dt closer than .0496, but...

*February 14, 2016*

**Algebra**

"trick" question the cosine of the complement equals the sine of the angle

*February 14, 2016*

**Calculus**

the description is of a hemisphere of radius 3 v = 2/3 π r³

*February 14, 2016*

**Chemistry**

density = mass / volume volume = mass / density v = 2.0E3 g / .785 g/mL = 2.5E3 mL careful with your units the mass is only 2 sigfig

*February 14, 2016*

**chemistry**

E = h * (c / λ) energy = Planck's constant * speed of light / wavelength λ = h * c / E h = 6.63E-34 J·s λ = 6.626E-34 * 2.998E8 / 3.211E-19 λ = 6.186E-7 m = 618.6 nm

*February 14, 2016*

**Algebra**

15 * 54 = s * 27

*February 14, 2016*

**chem**

STP corresponds to 0 ºC and 760 mm Hg the volume is directly proportional to the absolute temperature (ºK) and inversely proportional to the pressure v = 145 mL * (273 / 296) * (785 / 760)

*February 14, 2016*

**science**

yes, but the objects would not be the same size sticks could be two feet long or two meters long (same dimension, 2) but they are different sizes because of the units

*February 14, 2016*

**chemistry**

hope you mean cm^3 the molar mass of NaOH is 40 g so .05 moles in .25 L .2 M

*February 14, 2016*

**Physics**

if they pull in opposite directions with 180º between the forces the net force is zero if they pull in the same direction with 0º between the forces the net force is 200KN angles in between produce net forces in between

*February 14, 2016*

**chemistry**

the COMPOUND is carbon dioxide ... CO₂

*February 14, 2016*

**MATH**

the segment is 24 units long 7 + 5 = 12 24 / 12 = 2 so the ratio is (2 * 5):(2 * 7) or 10:14 the point is (0,6)

*February 12, 2016*

**college algebra2**

the area is proportional to the square of the side length 200 / (20^2) = 400 / L^2

*February 12, 2016*

**college algebra2**

the area is proportional to the square of the side length 280 / (18^2) = A / (6 1/4)^2

*February 12, 2016*

**math**

All, Sin, Tan, Cos...ASTC cos and tan are both >0 in quad I

*February 12, 2016*

**Math**

x^2 + y^2 = r^2 9 + 4 = 13 sin = y / r = -2 / √13 = -2√13 / 13

*February 12, 2016*

**Math**

sin^2 + cos^2 = 1 sin^2 + 2/9 = 1 sin^2 = 7/9 sin = ±√7 / 3

*February 12, 2016*

**Cal**

oops...got my axes swapped thanks, Cal

*February 12, 2016*

**Cal**

the shell method seems best the corners of the cross section are (4,0), (5,0), (5,.04), (4,.0625) not needed for solution, but helps to visualize the radius of the shell is x+2 volume = 2π * r * L * thickness = 2π * (x + 2) * (1 / x^2) * dx integration limits are 4 ...

*February 12, 2016*

**Math**

63/16 = tan(Θ) nearest degree (not tenths)

*February 12, 2016*

**maths**

better, but "motion"? measures of central tendency are: mean (average), median, and mode

*February 12, 2016*

**maths**

something is amiss in the question (besides spelling) if x is greater than 95 x+2 cannot be less than 72

*February 12, 2016*

**Math**

45º reference angle in quad II looks like A

*February 12, 2016*

**Math**

2π is a full circle...so they end at the same place π/6 + 2π = 13π/6 π/6 - 2π = -11π/6

*February 12, 2016*

**PHYSIC 220**

(a)i = [19.6 * cos(153º - 90º)] - [16.7 * cos(136º - 90º)] j = [19.6 * sin(153º - 90º)] - [16.7 * sin(136º - 90º)] k = 2.40 - 0 (b) d = √(i^2 + j^2 + k^2)

*February 12, 2016*

**Geometry**

(100% + 25%) / 100% = 5/4

*February 11, 2016*

**Physics**

watts = volts * amps = amps^2 * Ω 600 W = 6 V * 100 A = 100^2 * Ω A)energy = 1/2 * farads * (volts)^2 B)use C and R (Ω) to find the time constant of the circuit the capacitor is 95% discharged after 3 time constants

*February 11, 2016*

**algebra**

Use the rational zeros theorem to find all the real zeros of the polynomial function. Use the zeros to factor f over the real numbers. f(x)= x^4+6x^3-11x^2-24x+28 Molon

*February 10, 2016*

**Chem**

it looks red because it reflects the red wavelengths and absorbs the others

*February 5, 2016*

**Physics**

uniform acceleration means that the average speed is the numerical average of the initial speed and the final speed average speed ... (30 + 60) / 2 = 45 60 s in a min ... 60 min in an hr distance = 45 * 60 * 60 * 2 (meters)

*February 5, 2016*

**chemistry**

divide the total moles by the total L moles ... (.125 * .43) + (.017 * 1.8) Liters ... .125 + .017

*February 5, 2016*

**math**

24 * 3/8 = ?

*February 3, 2016*

**Math**

9.15 / 6.10 = 1.5

*February 3, 2016*

**math**

1 1/2 is six quarters 6 * 3 = ?

*February 3, 2016*

**Chemistry**

525 mL of .5 M solution contains (.525 * .5) moles of solute since you get 2 Cl-ions from each CaCl₂ you will need...(.525 * .5 * .5) moles of CaCl₂, dissolved in 525 mL of solution molar mass of CaCl₂ is 111 g (.5 * .5 * .525 * 111) g of CaCl₂

*February 2, 2016*

**Math**

6t + 1x + 3f = 35 + 10 = 45...(A) t + x + f = 13...(B) t = x...t - x = 0...(C) (A) - 3 (B)...3t - 2x = 6 subtracting 2(C)...t = 6 substitute back to find x and f

*February 1, 2016*

**science**

let [NO₂] equal 2x (2x)^2 = 0.0466 * (1.0 - x) 4 x^2 + 0.0466 x - 0.0466 = 0 you can use the quadratic formula to find x but answer 5 is the only one that makes sense

*February 1, 2016*

**math**

graph y = x^2 and y = x^3 (use fooplot_dot_com) the intersections are the solutions

*February 1, 2016*

**physics**

clarifying Rp = 12.5 * g Rq = 9.5 * g

*February 1, 2016*

**physics**

p and q are 4.0 m apart moments around q 4 p = (10 * 5) + (4 * 2) - (8 * 1) p = 12.5 Rp = 12.5 g moments around p 4 q = (8 * 5) * (4 * 2) - (10 * 1) q = 9.5 Rq = 9.5 g

*February 1, 2016*

**math**

there is no solution they have the same experience step value; but the starting salaries are different a Q teacher with equivalent experience will always have a $2000 higher salary than an R teacher

*February 1, 2016*

**Math**

step 6 x = y = 1 so division by x-y is division by zero a BIG no-no

*February 1, 2016*

**math (grade6)**

if Connor sold p fewer than Cassie then Cassie sold p more than Connor Connor sold 50 so Cassie sold 50+p

*February 1, 2016*

**Physics**

at one time constant (τ) the current is approx. 63% of max

*January 31, 2016*

**science**

not much info...

*January 31, 2016*

**math**

x² = 26² - 24² this is actually a Pythagorean triple...5-12-13 in this case...10-24-26

*January 28, 2016*

**Math**

4 x ≤ 17.50 - 4.50 4 x ≤ 13 x ≤ 3.25

*January 28, 2016*

**Math- Algebra**

8 n ≤ 60 dividing by 8... n ≤ 7.5

*January 28, 2016*

**Math**

14 gal and 25 mpg means you can drive 350 mi on a full tank...14 * 25 36 mi per day for 10 days is 360 mi so you have to gas up on the 10th day you can drive for 9 days before refueling

*January 28, 2016*

**Math**

8 * (30 + 4) = 240 + 32 = 272

*January 28, 2016*

**math**

9 char for the 1st position 9 for the 2nd 8 for the 3rd 7 for the 4th 26 for the 5th 9 * 9 * 8 * 7 * 26

*January 28, 2016*

**General Chemistry**

the partial pressures are the same ratio as the product moles from the reaction equation p CO₂ = 2/9 * 2.50 atm p N₂ = 1/3 * 2.50 atm p H₂O = 4/9 * 2.50 atm

*January 28, 2016*

**Physics**

the horizontal component of the stone's velocity is ...12 m/s * cos(30º) multiply by 8 s to find the distance

*January 28, 2016*

**Physics**

the speed is the vector sum of the plane and the wind north and east are perpendicular, so it's a right triangle s² = 499² + 87²

*January 28, 2016*

**Science**

looks like D

*January 28, 2016*

**science**

the normal force is...5 g cos(30º) the force along the ramp is ... 5 g sin(30º) 5 g sin(30º) = μ 5 g cos(30º) sin(30º) / cos(30º) = tan(30º) = μ

*January 28, 2016*

**Science**

good answer

*January 28, 2016*

**Chemistry 101**

one inch equals 2.54 cm a mL is the same as a cm³ the volume of the ball (in mL) is 4/3 * π * 1.26³ looks like a floater

*January 28, 2016*

**Algebra**

1/f = 1/o + 1/i 1/(1/4) = 1/(1/2) + 1/i 4 = 2 + 1/i i = 2

*January 28, 2016*

**Chemistry 101**

s.h. = 3450 / [10.65 * (99.9 - 28.5)]

*January 28, 2016*

**Chemistry 101**

mass = 1.2347 lb * 453.6 g/lb width = 1.256 ft * 30.48 cm/ft D = mass / [width * 12.6 * 45.6] the answer should be rounded to 3 significant figures

*January 28, 2016*

**Wave**

greater

*January 27, 2016*

**science**

the Sun appears to move across the sky because the Earth is rotating the Sun "moves" westward, so the Earth is rotating eastward

*January 27, 2016*

**Math**

bike...d = 6t ... d/6 = t bus... 26 - d = 30 (t - 1/3) substituting...26 - d = 30 (d/6 - 1/3) 26 - d = 5d - 10 36 = 6d

*January 26, 2016*

**Physics**

flying N at 250 km/h for 30 min should put him at 125 km N of the start the wind has pushed him 75 km N and 40 km W in 30 min so the wind is blowing 150 km/h N and 80 km/h W Vw² = 150² + 80² the tangent of the angle (west of north) is...8/15

*January 26, 2016*

**Physics**

the velocities add as vectors they are perpendicular to each other v² = 6² + 4²

*January 26, 2016*

**Science**

protons are positively charged so it would repel electrons are negatively charged so it would attract

*January 26, 2016*

**Physics**

the radius of the Earth is 6.37E3 km gravitational force is inversely proportional to the square of the distance 9.81 * (6.37E3)² = 6.44 * (6.37E3 + h)²

*January 26, 2016*

**Coulomb's Law**

the force is inversely proportional to the square of the distance (inverse-square relation) the new force is 4 times the original 1 / (1/2)² = 1 / (1/4) = 4

*January 26, 2016*

**math**

the change is $5 that is 25% (5/20) of the starting value

*January 26, 2016*

**Math**

losing time means running too slow when an hour has passed, the clock has only moved 45 min it is running at 3/4 speed (45/60) so when it shows an hour has passed, an hour and 20 min (4/3 hr) has actually passed the correct time is...10:20 AM

*January 26, 2016*

**Physics**

pressure is measured in Newtons per square meter or Pascals 20 m below the surface, there are 20 cubic meters of water stacked up 20,000 kg * 9.8 m/s² = 2.0 x 10⁵ N the water pressure is...2.0x10⁵ Pa the total pressure is...3.0x10⁵ Pa

*January 26, 2016*

**Physics**

t equals the fall time 0 = -4.9 t² + 1000 horizontal distance to target d = t * 200 km/hr convert km/hr to m/s the tangent of the angle is the height of the plane, divided by the horizontal distance to target

*January 26, 2016*

**science**

the kinetic energy of an object is equal to one half of the product of the object's mass and the square of its velocity KE = 1/2 m v²

*January 26, 2016*

**physics**

charge = capacitance * voltage coulombs = Farads * volts

*January 26, 2016*

**Chemistry**

each molecule of ammonium nitrate yields one ammonium ion and one nitrate ion so, twice the number of moles that you started with

*January 26, 2016*

**Mathematics**

draw the picture... d = h / tan(52º)

*January 26, 2016*

**Science**

a galvanometer measures current an electromagnet is the active element try B.

*January 26, 2016*

**physics**

see physics/tom about ten questions below this

*January 26, 2016*

**physics**

(a) v = 100 m / 8.70 s (b) constant acceleration (from zero) means that the average velocity during the acceleration phase is half of the final velocity (v/2) t + v (9.58 - t) = 100 m plug in v and solve for t (c) average acceleration is v/t

*January 26, 2016*

**Science**

the force (in Newtons) equals the product (multiply) of the charges (in Coulombs) divided by the distance (in meters) squared f = q₁ q2 / d²

*January 26, 2016*

**math**

this is true because a diameter is a straight line connecting two points on the circumference of a circle

*January 25, 2016*

**Chemistry**

the balanced equation reveals the answer C₃H₈ + 5 O₂ ---> 3 CO₂ + 4 H₂O looks like 6

*January 25, 2016*

**phy 231**

3.05 = -1/2 g t^2 + v sin(α) t + 2.10 19.2 = v cos(α) t plug in sin and cos values solve the system for v (and t)

*January 24, 2016*

**Maths**

5a + 10d + 7a + 21d = 167 10a + 45d = 235 solve the system for a and d S₂₀ = 20a + 190d

*January 24, 2016*

**Physics**

h = -1/2 g t^2 + 100 t + Ht 0 = (-4.9 * 25^2) + 2500 + Ht

*January 24, 2016*

**science**

to double the volume at a constant pressure, you have to double the ABSOLUTE (Kelvin) temperature 0ºC = 273.15ºK

*January 24, 2016*

**statics**

a score of 105 is one standard deviation above the mean the rule says that 68% of a normally distributed population lies within one standard deviation of the mean...half above the mean and half below so 34% are within one standard deviation above the mean this means that 16% ...

*January 24, 2016*

**ALgebra**

t for ten and w for twenty t + w = 54 10 t + 20 w = 780 solve the system

*January 21, 2016*

**Science**

you don't have any units ... and Mars is more than a light-second away

*January 21, 2016*

**Physics**

let's call right positive momentum is conserved (5 * 4) - (2 * 6) = (5 * .8) + (2 * v) 8 = 4 + 2v

*January 21, 2016*

**physics101**

how far from the end of the platform?

*January 21, 2016*

**Chemisty**

yes, it's A because the specific heat is lower, it takes less heat to raise the temperature a greater temperature change for a given amount of heat means that the temperature changes faster

*January 21, 2016*

**physics**

the desired acceleration is twice the gravitational acceleration, in an upward direction so the required force is 3 g's f = m a = 5 * 30 = 150 N

*January 20, 2016*

**Chemistry**

Cl is -1, so the Fe is +2 or +3

*January 19, 2016*

**Physics**

gravitational force parallel to the plane is...m * g * sin(30º) If the efficiency of the plane is 75%, then the coefficient of friction is .25 the normal force is...m * g * cos(30º) so the minimum force is [m * g * sin(30º)] + [m * g * cos(30º) * .25]

*January 19, 2016*

**math**

let t equal the fill time the pipes each fill a fraction of the pool the fractions sum to one (the whole pool) one fraction is t/8 the other is t/12 t/8 + t/12 = 1 24 is the LCD 3t + 2t = 24

*January 19, 2016*

**Chemistry**

it takes 4.179 J of heat to change the temperature of 1 g of water by one ºC 209 / (10.0 * 4.179) = temp. change looks like about a 5ºC increase

*January 19, 2016*

**Chemistry**

1 L of .1 M contains .1 moles volume = .1 mole / 12.1 mol/L .1 / .0121 mol/ml = ?

*January 19, 2016*

**Chemistry 101**

there are 2.54 cm in an inch a cm^3 is the same as a mL volume = π * .5^2 * 2.5 * 2.54^3 ...the result is in cm^3 multiply the volume by the density (.26)...that is the mass in g round the result to TWO sig fig ...that is the limiting number in the density value

*January 19, 2016*