# Posts by Scott

Total # Posts: 2,323

**Math (Physics)**

Rn = n^2 * R1 2.50E-3 m = n^2 * .53E-10 m En = (13.6 / n^2) eV

**No one is helping me :/ ??**

3 as an asymptote means that is the value that the function approaches as x goes to infinity

**college algebra**

only if the system is dependent ... which it isn't

**college algebra**

subtract the 2nd equation from the 3rd equation solve the two remaining x and z equations with substitution or elimination x + 2z = 5 3x - 4z = 15

**Physics**

a) 10/12 = (1/2)^(t/5700) [log(10/12)] / log(1/2) = t / 5700 b) use t from a) c = 12 * (1/2)^[(t+100)/5700] c / 12 = (1/2)^[(t+100)/5700]

**math**

2 log(x) + log(4) + 1 = 2 OR 40 x^2 = 100

**physics**

the resistance is directly proportional to ... length and specific resistance it is inversely proportional to the cross sectional area ... (square of the diameter) 4? * (2P / P) * (d / 2d)^2 * (3L / L)

**Algebra 2**

looks good

**Math**

the "degree" is the value of the largest exponent

**Physics**

the range formula is d= (v^2 / g) sin(2?)

**Math**

a = 24000 [1 + (.04 / 12)]^(30 * 12) 4% interest, compounded monthly

**Math- PLEASE HELP. I DONT UNDERSTAND THIS QUESTION**

A = 1/2 b h solve this for b

**Science**

looks good

**Physics**

with g=10 the highest it gets is 5 m at t = 1 s

**physics**

force / distance

**physics 10**

the given explanation is reversed when the coefficient is changed by moving the decimal point, the exponent is changed to keep the overall value the same bigger coefficient means smaller exponent ... and vice versa

**algebra**

try fooplot online

**MATHS**

C is a right angle (corner of a rectangle) the bisector makes a 45º angle so CBX is an isosceles right triangle ... BX = BC

**math**

how many possibilities in each subgroup? ... 6Cn how many ways to combine the different subgroups?

**physical science**

speed is frequency multiplied by wavelength 250 waves per second each wave is 6.0 meters long

**Physics**

1 W·s = 6.24E18 ev

**Physics**

look up "heat of fusion" for lead it's like the specific heat, but for melting

**math**

let's say that the cube has an edge length of 3 units so the blue surface area is ... 6 * 3^2 each of the smaller cubes has an edge length of 1 unit so their collective surface area is ... 27 * 6 * 1^2

**college algebra**

w^2 + (180/2)^2 = (240/2)^2

**story problem**

the wires form a 30-60-90 right triangle, with the ground as the hypotenuse both of the smaller triangles are similar to the large triangle the length of the 2nd wire is half of the distance between the wires use Pythagoras or trig to find the height of the pole

**Physics**

cool steam to 100ºC condense steam to water cool water to 80ºC two specific heats (water and steam) ... one heat of vaporization

**physics**

heat ice to 0ºC melt ice heat water to 100ºC boil water heat steam to 125ºC specific heats - ice, water, steam ... heats of fusion and vaporization

**math**

feet, yards, meters

**Science**

m * g * h / t answer is in Watts

**Math**

complementary angles sum to 90º t < 2 s

**Math**

the (3x+12) term from Monica's factoring can be factored again into 3(x+4), leading to Ashely's result

**Math**

the numbers in the binary factors are factors of the constant term of the quadratic (-24) the sum of the numbers is the coefficient of the 1st order term of the quadratic (-5) the numbers -8 and 3 are factors of -24 that sum to -5 so the factors of the quadratic are ... (x - 8...

**Algebra**

they each do a fraction of the job (t / 40) + (t / 60) = 1

**Science**

don't know if you've seen video of a bouncing ball, but the bottom side flattens to provide the push for the bounce

**physics**

is relative mass the same as specific gravity? if the s.g. is 19, then the apparent mass (weight) in water is ... (19 - 1) g/cm^3 * 20 cm^3

**Physics**

divide the distance by c (speed of light) c = 3.00E8 m/s the frequency is not relevant

**physics**

heat lost by water = heat gained by unknown your method is fine

**Physics**

without knowing the speed of the train, there are no exact answers for b, c, and d you are correct for a b will hear a higher frequency c will hear a lower frequency d will hear the highest frequency ... the train (whistle) is moving toward the cliff, so the echo will be a ...

**Math**

The scores on the GRE are normally distributed with a mean of 541 and a standard deviation of 89. Use the 68-95-99.7 rule to find the percentage of people taking the test who score between 363 and 541

**Linear Algebra**

this should help p = 800 (1 - 0.13)^5

**math**

half of the numbers on the cube are even so a fair cube should have half of the outcomes even

**Algebra**

0 = -(x+2)^2 + 3 (x+2)^2 = 3 x + 2 = ±?3 x = -2±?3

**Science**

large nuclei split (fission) into smaller nuclei that have less binding energy the lost binding energy converts to heat through various processes

**math**

v = 4/3 ? r^3 through the magic of algebra... r^3 = 3/4 v / ? take cube root of both sides

**Calculus**

OOPS... missed the "anti" part that is the derivative

**Calculus**

4 (x^2 + 1)^-1 4 * -1 * (x^2 + 1)^-2 * 2x -8x / (x^2+1)^2

**chemistry**

diffusion rate is inversely proportional to the ? of the molecular weight CO2 / SO2 = ?(64.1 / 44)

**pre-calc**

inspection shows 1 as a root (zero) so (x - 1) is a factor dividing p(x) by (x - 1) will leave a quadratic that can be broken down

**Chemistry**

what reaction??

**algebra**

your solution looks fine

**Physics**

figure??

**Pre calc**

sin(?) = -5/13 , cos(?) = -12/13 cos(?) = .3?10 sin(? ? ?) = sin(?)cos(?) - ... cos(?)sin(?)

**Science**

increasing the (absolute) temperature and decreasing the volume will both cause an increase in pressure p = 740 torr * [(50 + 273) / (25 + 273)] * (356 / 250)

**Science**

d = 1/2 a t^2 1/2 a(12^2 - 8^2) = 64

**physics**

barrel length is not a factor kinetic energy = 1/2 * .003 * 400^2 units are Joules

**Trigonometry**

construct perpendicular bisectors on the two shorter sides (non hypotenuse) the bisectors will intersect the hypotenuse at the vertices of the two isosceles triangles the common side for the triangles is the line from the intersection to the right angle

**Chemistry**

the change in energy level is ... energy = Planck's Const. * freq the Balmer Series starts at n=2 look at the energy levels to see how far the electron jumped

**Math**

8000 * 3.25x10^-22 g = 2.50x10^-18 g

**Maths**

a 2x3 grid (6 dots) has 15 pairs each of the pairs can be an edge or a diagonal some squares involve 4 dots ... some, only two

**physics**

a = 9.8 m/s / 5 s f = m a = m g ? a = g ? 9.8 m/s / 5 s = 9.8 m/s^2 * ?

**physics**

the forces are vectors that add by Pythagoras 60^2 + 80^2 = 100^2

**Physics**

the plane is moving inside an air mass that is moving relative to the ground the ground speed is the sum (vector) of the two speeds 345 kph, S40ºW ... 345 cos(40º) S ... 345 sin(40º) W 85 kph, NW ... 85 cos(45º) N ... 85 sin(45º) W find the vector sum ...

**stem**

m * g * h 65 * 9.8 * .2

**Chemistry**

p v = n r t ... v = n r t / p make sure the r value has the correct units

**physics**

m * g * h

**Chemistry Homework**

55.6 moles of H2O per liter x / (55.6 + x) = .25 x is the CO2 molarity

**Chemistry Homework**

mole fraction means .25 moles of CO2 for each mole of solution (along with .75 moles of H2O) molarity means moles of CO2 per LITER of solution so, how many moles of water in a liter?

**Hard Pre-Algrebra question**

the prism is 20 cubes by 17 cubes by 8 cubes cubes = 20 * 17 * 8 vol = 2 1/2 * 2 1/8 * 1 in^3

**further algebra**

it's a convergent geometric series, so you can find the sum the sum, minus 30, is the total rebound distance s = a / (1 - r) = 30 / (1 - 4/5)

**Math**

[(3 * 37) + 41] / 4 = ?

**This isn't about school**

as was stated in an earlier post we try to HELP with work, not do the work if you need to post a question here, you should be learning something from the question

**Calculus**

d/dx sin(a) = da/dx cos(a) the derivative of the sine is the cosine but the argument may also have a derivative

**Physics**

the wall is on the axis of symmetry of the parabola his initial vertical speed is ... 25 m/s * sin(45º) ... gravity slows him down to zero at his vertical peak ... the times is ... 25 * sin(45º) / 9.8 his horizontal speed is ... 25 m/s * cos(45º) ... use the ...

**Physics**

[g * (1.9 - .25)] / (.775 - .175)

**MATH**

.9 x + .4(100 - x) = .7 * 100

**Math ASAP**

yes the resulting triangles can be a range of sizes, depending on the orientation of the cut

**Algebra 1**

what's the procedure for rounding to a tenth? the egg must be ? 1.55, and < 1.65

**Math**

180 * (1 + .07)^12

**math**

remember, there is a hierarchy for operations PEMDAS

**math**

(27) - (-36)

**SCIENCE CHECK!**

photosynthesis is the process by which plants convert carbon dioxide and water into oxygen and carbohydradtes

**Geography (w/ geometry)**

the shadow is 4 times the length of the bridge (bldg height) / shadow = tan(sun elev)

**Math Ratios**

3 x = x + 8 ... x = 4 1 x + 2 x + 3 x = ?

**Algebra Concentration Problem**

x + y = 10 .65 x + .30 y = .40 * 10

**math**

it takes 600 worker-weeks (like man-hours) to build 4 mi of highway 150 worker-weeks per mile so 2400 worker-weeks can build ... 2400 / 150

**Math**

it's full at 10 half full at 9:59 a quarter full at 9:58

**maths**

SOHCAHTOA and the inverse functions draw the right triangle find the hypotenuse (Pythagoras) write the side ratios for the functions

**math**

(440 / ?) + (2 * 14)

**Chemistry**

.755 M * 10.9 / (10.9 + 57.6)

**scientific notation**

it's correct

**Physics**

5 rps to 25 rps is 20 rps in 10 s 2 rps/s = 4? rad/s^2 average rpm is 900 or 15 rps so 150 rev

**Chemistry**

Cl2 is the limiting reactant divide by the molar mass to find the number of moles m.m. Cl2 is 70.9 g

**chemistry need help so bad seriously help plz**

1 / ? = R [(1 / n?^2) - (1 / n?^2)] R = 1.097 x 10? m?¹ the starting principle quantum number (n?) for the Paschen Series is 3 the number (n?) for the 3rd line is 6

**math**

169 has an integer SQUARE root it is not 15

**math**

FOIL the two binomials

**MATH URGENT HELP!**

4% means 1% per quarter (compounding period) 10 yr is 40 quarters A = 5000 (1 + .01)^40

**Algebra 2**

180º is the negative x direction x = -12.5 , y = 0 (12.5,0)

**Science**

the trains are closing at 100 kph ... so it takes them 1 hr to pass the plane flies 90 kph for 1 hr

**Algebra**

should be .94 in last eqn...not .96

**Algebra**

10000 (1 + .08)^t = 33000 (1 - .06)^t log(10) + t log(1.08) = ... log(33) + t log(.94) t [log(1.08) - log(.94)] = ... log(33) - log(10) t = log(33 / 10) / log(1.08 / .96)