# Posts by Scott

Total # Posts: 2,574

**Chemistry**

these values are negative logarithms of the concentrations so a bigger number means a lower concentration

**Science**

work = f * d = 60 * 2 = 120 J power = work / time = 120 / 10 = 12 W work is in Joules and power is in Watts

**homework**

36 m times 4 lengths per day times 7 days per week times 4 weeks

**Science**

the mass (in kg) multiplied by the gravitational acceleration (in m/s^2) gives the weight in N (Newtons) w = .0585 kg * 9.8 m/s^2 w = .04593 kg * 9.8 m/s^2 the g value is 2 sig fig, so that is what the answer will have

**Chemistry**

Thanks

**Chemistry **

Tooth enamel consist mainly of hydroxyapatite (Ca5(PO4)3(OH). When tine (II) Flouride is added to toothpaste it reacts with the enamel to product a more decay-resistant material fluorapatite (Ca(PO4)3F. The by-products of this reaction are tin (II) oxide and water. What mass ...

**Math**

adding the equations ... to eliminate y 3x = 3 solve for x, then substitute back to find y

**Calculus**

h = highway distance from intersection d = auto-to-farmhouse distance by Pythagoras ... d^2 = h^2 + 6^2 differentiating implicitly ... 2 d dd/dt = 2 h dh/dt dd/dt = h / d * dh/dt

**Science**

barium carbonate in the same family as calcium carbonate (chalk)

**pre calculus**

(a) time up = time down ... = 320 fps / 32 ft/s^2 (b) the velocity at a given height is the same upward and downward EXCEPT for the direction the max height is 1600 ft, which is reached in 10 sec ... the velocity is zero at this point 1584 ft is one sec below the max ... 9s &...

**Physics**

the time to fall is ... t = ?(2 * 54 / g) speed off cliff = 130 m / t

**Pre-Algebra**

4/3 * ? * r^3 = ? * r^2 * 3 4/3 * r = 3

**Algebra1**

-8 * 6^2

**Algebra1**

100,350,000 * (1 + .017)^15

**Science**

t = 8.9 / 4.57 stopping distance = (8.9 / 2) * t

**Physics**

t = d / r across ... t = d / 2 back ... t = d / 8 total time ... d/2 + d/8 = 5d/8 total distance ... d + d = 2d average speed ... 2d / (5d/8) = 16d / 5d

**Math**

50h + 25(3h) + 10(12h) + 5(12h + 2) = 925 50h + 75h + 120h + 60h + 10 = 925 305h = 915

**Chemistry **

Silicon Carbide, SiC, is prepared by heating silicon dioxide in the presence of graphite. Carbon dioxide is the by-product of the reaction. How many grams of silicon carbide can be formed from the reaction of 50.0 grams fo graphite with 50.0 grams of silicon dioxide?

**Chemistry **

A scientist studying the reaction between decaborane (B10H18) and oxygen mixed 1.00 x 10^2 grams of decaborane with 2.75 x 10^2 grams of oxygen. Compute the masses of all substance present after the reaction went ot completion, generating B2O2 and water as the only products.

**Math**

you've got x and y switched ... and the rate of ascent is the slope the right equation will give the right answer

**Math**

1st one is correct the division hint is for the 2nd

**Math**

one out of two if something goes into something else "evenly" (wholly), then ...

**math**

dh/dt is the velocity (1st derivative) v(t) = -32t

**physics**

hydraulics? the force multiple is the ratio of the piston areas f * (180 / 2)^2 = 2400 * g

**Physics**

the density of air decreases with altitude the balloon stops rising because the density of the gas inside is close to the ambient air density the weight of the balloon itself also contributes to the loss of bouyancy

**ADVANCED LEVEL PHYSICS**

after 4 s, the velocity is 4*a after 5 s, the velocity is 5*a the average velocity in the 5th sec is ... (5a + 4a) / 2 = 4.5a 4.5a = 36 ... a = 8 m/s^2

**Algebra**

w + j > 18 w/3 + j/6 < 5 ... 2w + j < 30 walk 1 hr, jog 3 hr

**Math**

no 27 + 33 = 60 they will end up with two lengths of fence with no space in between

**word problem**

(49 - 9) / 4 = (85 - 9) / 4 =

**Math**

2 sin^2 - sin - 1 = 0 (2 sin + 1)(sin - 1) = 0 2 sin + 1 = 0 ... sin = -1/2 sin - 1 = 0 ... sin = 1

**Math**

80 cubes long 8 cubes wide 13 cubes high

**maths**

n^2 + 1/n^2 = 7 n^4 + 1 = 7 n^2 ... n^4 - 7 n^2 + 1 = 0 let k = n^2 k^2 - 7k + 1 = 0 use quadratic formula to find k n = ?k

**Maths**

z = 7/9 c

**math**

the east component is ... 10 cos(30º) the north component is ... 10 sin(30º) - 4 speed = ?[(east)^2 + (north)^2] tan(?) = north / east ? is degrees north of east

**chemistry**

the molar mass of Fe is 55.8 g [98.7 / (2 * 55.8)] * 852 kJ

**physics**

the ball is pulled back from the lowest point, and gains gravitational potential energy this energy becomes kinetic energy when the ball is released ... it is maximum at the low point m g h = 1/2 m v^2 ... v = ?(2 g h) use trig to find the height above the low point

**Algebra**

9 / .75 = x / 7.5

**College Algebra**

(x * .05) + [(10000 - x) * .06] = 550

**Chemistry**

hydrogen and hydroxide ions are neutralizing each other acid vol * molarity * hydrogens = ... base vol * molarity * hydroxides 26.3 * x * 2 = 17.45 * .425 * 1

**math**

p log(8.2) = q log(10.5) p / q = log(10.5) / log(8.2)

**Math :(:( Totally stressing ouuut ned help now.**

translation moves the object, but it maintains its orientation reflection or rotation can result in the point being up

**math help now plez**

type the url (web address) for the figure

**High School Geometry**

this is a 30-60-90 triangle m?L = 30 ° ... AK is the side opposite AL (the hypotenuse) is twice AK KL is AK times ?3 the area is 1/2 the product of the two perpendicular sides

**Math**

9 m x 6 m = 54 m^2 4 m x 4 m = 16 m^2

**Biomechanics**

1.5 laps is 600 m 600 m / 77 s = 7.8 m/s it's a straight forward calculation typo somewhere?

**stats**

the dice are independent chance (probability) of a 5 is ... 1/6

**physics help please**

the difference in the path length between the direct and reflected sound should be an odd half wavelength to facilitate cancellation ... 1/2, 3/2, 5/2... the speed of sound is 340 m/s so the wavelength is 340/440 m the diagram is an isosceles triangle with an altitude of 2 m...

**math need help now**

as bob says "all REGULAR n-gons are similar" C for sure (they're regular) D doesn't say "regular"

**math**

you're looking for an area of 80 try C

**Physics**

vol = m / d = 20 kg / 20Mg/m^3 = 1 L the stone displaces 1 L of water with a mass of 1 kg the stone's weight is ... 19 * g

**math**

pay = [$.01 * 2^(day)] - $.01

**Physics **

did your G have the right units? you are correct that either equation should work Fg = Fc ... in orbit ... recalculate, and watch your units

**Science**

blood comes from the body ... goes to the lungs ... comes back from the lungs ... goes back out to the body the blood drops off carbon dioxide and water in the lungs and picks up oxygen, which is carried out to the body look up the exact flow through the heart chambers ...

**physics**

the surface is frictionless, so T is providing acceleration to the boxes the accelerating force is transferred to the small box by friction between the boxes at some point (as T increases), the frictional force will not be enough to provide the necessary acceleration and the ...

**chemistry**

.100 L * .10 M/L = .010 M .010 M / 4.0 M/L = ?

**chemistry**

each mole of butane yields 5 moles of water a mole of gas at stp is 22.4 L 10/22.4 * 5

**probability**

this is a binomial result ... win or not win P(w) = .15 , P(n) = .85 (n + w)^10 ... you want the 3rd term 10C2 * .85^8 * .15^2

**Physics**

the acceleration is ... g sin(38.0º) d = 1/2 a t^2 ... t = ?(2d / a)

**Chem**

you need to combine the given reactions ... some partial and/or reversed ... to get the desired reaction 2CO2 + H2O --> C2H2 + 5/2 02 ?H = 1300 kJ 2C + 2O2 --> 2CO2 ?H = -788 kJ H2 + 1/2 O2 --> H20 ?H = -286 kJ add the 3 reactions, along with the ?H's ... cancel ...

**Math**

1 cm on the original is 20 cm on the transfer

**chemistry**

not enough nitrogen a mole of nitrogen is needed for every 3 moles of hydrogen

**math**

tan(?) = 250/170

**Math**

v = 24 (1 + .06)^385

**physics**

2 * vertical velocity / g 16.7 * ?2 / 9.81

**Algebra**

(a) m = 500 (1 + .015)^t (b) 800 = 500 (1 + .015)^t ... 1.6 = 1.015^t ... log(1.6) = t log(1.015) ... [log(1.6)] / [log(1.015)] = t

**Algebra - PLEASE HELP!**

231 = -17.5x2^ - 138.5x - 27 462 = -37 x^2 - 277 x - 54 0 = -37 x^2 - 277 x - 516 use quadratic formula to find x

**probability**

there are 9 pairs of cards that differ by one ... 1-2, 2-3, 3-4, etc. there are 10C2 possible pairs ... 45 so the probability of a pair differing by one is 9/45 or .2 ... by more than one is (1 - .2) = .8 3 cards contain 3 pairs .8^3 = .512

**physics**

m g h = 1/2 m v^2 ... v = ?(2 g h)

**physics**

it's a fraction of a mole ... 9.1E5 / 6.02E23 multiply the fraction by the molar mass

**physics**

60 sec in a min 2.54 cm in an inch 9.843E4 ft/min * (1 min / 60 s) * ... (12 in / 1 ft) * (.0254 m / 1 in)

**physics**

f = m a = 2E3 kg * ... [(20 m/s - 5 m/s) / 4 s] answer is in Newtons

**Algebra2**

an = 13n - 8

**Physics**

convert mph to m/s convert cg(?) to kg K.E. = 1/2 m v^2

**physical science**

Joules of energy required ... 202 * (95.6 - 22.0) * 4.18 divide by heater wattage ... 1 watt = 1 Joule per second divide by 60 ... sec to min

**Physics**

friction

**science**

free fall...starting from rest d = 1/2 g t^2 ... plug in the times, and find the difference in the distances the 1st body will always be going faster than the 2nd, so the distance between them is always increasing

**Math**

the edge length is the cube root of the volume 8 in this case

**Math**

not enough information

**Maths**

the distance between the centers of the two outer circles is 4 they are in the diagonal corners, and their centers are ?2 from the corners so the diagonal of the square is ... 4 + 2?2 dividing by ?2 to find side length ... 2 + 2?2 squaring ... 4 + 4?2 + 4?2 + 8 = 12 + 8?2

**Math**

order counts 6P3

**physics**

the work ... 7.6N * 8.6m ... is equal to the block's KE 1/2 * 0.50 * v^2 = 7.6 * 8.6

**Math 125**

sometimes just using numbers will clarify for 2000 people ... 10 have the virus ... 8 will test pos ... 2 will not ... 1990 do not have the virus ... 199 will test pos a) 207 people test pos ... 8 of them have it ... 8/207 = .0386 b) 1793 people test neg ... 2 of them have it...

**physics**

20^2 = 10^2 + v^2 sin(?) = 10/20 ... north of west

**College Chem**

heat gained by water equals heat lost by metal 50.0 * (t - 20.0) * 4.182 = ... 1000 * (100.0 - t) * 0.50

**Physics**

you know the size of the disk, and the material (aluminum) calculate the volume and look up the density

**Physics 202-help**

15/3 = 5 ... storm distance in km 15s * 343m/s = theoretical distance the time for the light to travel is below the sig fig of the other measurements ... it can be considered instantaneous

**backwards math**

(6 + 6 - 5) * 4

**Algebra**

u = t + 7 10u + t = 3(10t + u + t + u) ... = 33t + 6u 4u = 32t solve the system by substitution or elimination

**math**

x (154) + (40 - x)(170) = 40 (160)

**Math**

v / 125 = [v / (125 + 25)] + 4/3

**Physics**

1) the sound goes over and back ... 2 w =5.7 * 343 2)velocity = frequency * wavelength ... v = (2.22 / 7.59) * .168 m

**Physics**

3 s measures the km to the lightning 5 s measures the miles

**Algebra**

(k - 10)(k - 2) (2x + 7)(3x - 2)

**maths**

45 * (1 + .10)^20

**too-hard probability sir damon/reiny/steve help**

"you can lead a horse to water...but you can't make him drink"

**too-hard probability sir damon/reiny/steve help**

this is binomial...with a twist P(b) = .4 , P(w) = .6 (b + w)^4 b^4 + 4 b^3 w + 6 b^2 w^2 + 4 b w^3 + w^4 P(w ? 0) = 1 - P(b = 4) = 1 - .4^4 P(b = 2) = 6 * .4^2 * .6^2 divide to find the conditional

**Physics**

the given data is unrealistic please check it

**physics**

the ball is uniformly accelerated by gravitational force the velocity is zero at the peak 1.5 s before the peak, the velocity is ... 1.5 * g upward 1.5 s after the peak, the velocity is ... 1.5 * g downward

**PreCalc**

18 t + 5 t - 5 = 12

**Algebra 2**

x y = k