Wednesday

December 7, 2016
Total # Posts: 1,559

**Chemistry**

sorry...should be 2 H₂

*February 16, 2016*

**Chemistry**

Ca is a +2 ion so 2 OH (just like the 2 H) CaH₂ + 2 H₂O --> Ca(OH)₂ + H₂

*February 16, 2016*

**Physics**

gravitational potential energy is converted to kinetic energy m g h = 1/2 m v² 9.8 * 1.8 = v² / 2

*February 16, 2016*

**physics**

the vertical launch velocity is ... 33 sin(12º) 0 = 1/2 g t² + [33 sin(12º)] t + 23 use the quadratic formula to find t ...you want the positive solution g = 9.8 m/s²

*February 16, 2016*

**chemistry**

the spectrum is the result of hydrogen's electron transitioning between energy levels the levels are fixed ... quantized (per bob)

*February 16, 2016*

**Chemistry: stoich**

molar mass of O₂ is 32 g 5 moles O₂ yields 4 moles H₂O

*February 16, 2016*

**Chemistry**

answered

*February 16, 2016*

**physics**

momentum is conserved x-component ... -8.80 [4720 / (4720 + 1180)] y-component ... -1.45 [1180 / (1180 + 4720)] v = √(x^2 + y^2) the tangent of the reference angle in quad III is ... y/x

*February 16, 2016*

**Chemistry**

the molar mass of O₂ is 32 g 3 moles of oxygen produce 2 moles of iron oxide (2.50 / 32)* 2/3 = moles of Fe₂O₃ the molar mass of Fe₂O₃ is 159.7 g

*February 16, 2016*

**Math HELPP!!**

obtuse? that means an angle greater than 90º B is correct

*February 16, 2016*

**Math HELPP!!!!**

correct

*February 16, 2016*

**Math. PLZZZ HELP ME!!!**

or B or C... not enough info in the question TOO GENERAL

*February 16, 2016*

**Math. PLZZZ HELP ME!!!**

a quadrilateral with opposite sides equal and parallel is a parallelogram the 1st three answers are various types of parallelograms a trapezoid is not

*February 16, 2016*

**Science**

the same side of the moon always faces the Earth because the moon's rotational period is equal to its orbital period if the moon had a rotational period different from its orbital period, then different sides of the moon would be facing the Earth at different times

*February 16, 2016*

**Physics**

the horizontal component of the force is... f cos(Θ) as you say... a = [f cos(Θ)] / m

*February 16, 2016*

**Physics**

no friction, so why is gravity involved? f = m a 89 = (8 + 33 + 49) a

*February 16, 2016*

**Physics**

so the maximum load (cabin plus cargo) is 3300 kg the tension is the force that will accelerate the load to .68 m/s² this is against gravity so the tension overcomes gravity (mg) PLUS accelerates the load t = m g + m a = m (g + a) ...= 3300 (9.81 + .68)

*February 16, 2016*

**physics**

work (energy) is equal to the product of the force and the distance the energy is the same for both

*February 16, 2016*

**AP Physics 1**

.12 * 5.0 * 20.0 * 220 / 1000 A * V = watts watts * 5 = watt·hr dividing by 1000 gives kw·hr

*February 16, 2016*

**physics**

constant velocity means zero acceleration f = m a f = m * 0 f = 0

*February 16, 2016*

**Math**

5280 feet in a mile 12 inches in a foot the long skinny right triangle base = half mile hypotenuse = half mile plus half inch height = √(hypot^2 - base^2) almost 15 feet

*February 15, 2016*

**chemistry**

the reaction equation is in moles so you need to convert grams of iron oxide to moles the molar mass is 159.7 (two iron plus 3 oxygen) 14.7 g / 159.7 g/mol = .092 moles the reaction equation shows 3 moles of carbon dioxide for each mole of iron oxide so .092 * 3 = .276 moles ...

*February 15, 2016*

**URGENT! Due soon and I used 8 of 10 attempts**

be careful of significant figures,,,

*February 14, 2016*

**URGENT! Due soon and I used 8 of 10 attempts**

.5^n = .145 n = log(.145) / log(.5) = 2.786 2.786 * 5730 = 1.60 x 10^4

*February 14, 2016*

**Physics**

so M2 hangs over the side? f = m a ... a = f / m ... the blocks have the same a (g - t) / M2 = t / M1

*February 14, 2016*

**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*