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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)

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