Monday

August 29, 2016
Total # Posts: 1,227

**Science**

going directly from a solid to a gas is called sublimation
*July 6, 2016*

**Physics**

heat = mass * temp change * specific heat make sure the units are consistent
*July 6, 2016*

**Calculus**

the horizontal components of the two ropes' tensions balance each other the combined vertical components equal 400 N sin(60º) = T1v / 400 N T2v = 400 N - T1v cos(60º) = T1h = T2H T2 = √[(T2v)² + (T2h)²]
*July 6, 2016*

**Chemistry**

the iron is oxidized the hydrogen is reduced
*July 6, 2016*

**Physics**

80 C / .001 s = 80000 C/s = 80 kA
*July 6, 2016*

**Math (Quadratic Equations)**

(1 / A) + (1 / B) = 1 / 12 (1 / A) + [1 / (A - 7)] = 1 / 12 12 A - 84 + 12 A = A * (A - 7) 24 A - 84 = A² - 7 A 0 = A² - 31 A + 84 factor the quadratic to find A
*July 6, 2016*

**Math**

-3 is not a root the roots are ... -3±i 4, -3+i, -3-i
*July 6, 2016*

**Math**

the highest exponent is the order...and the number of roots a root is a value that makes the function equal to zero you can test values for roots ... 4 works here divide the function by (x - 4) to factor out the known root ... this leaves a quadratic ... use the quadratic ...
*July 6, 2016*

**algebra 2-1**

30 c + 40 t = 270 ... 3 c + 4 t = 27 12 c + 15 t = 105 solve the system 12 c + 16 t = 108
*July 6, 2016*

**Analytic geometry**

this is a line that is the perpendicular bisector of the line between the given points
*July 6, 2016*

**Analytic geometry**

this is an ellipse the two given points are the foci
*July 6, 2016*

**CHEMISTRY**

the 64 is a good clue the mass ratio of the components is constant amu, or grams, or tonnes ... same ratio
*July 5, 2016*

**Physics**

average velocity is ... (4 + 14) / 2 d = v t
*July 5, 2016*

**Physics**

the horizontal velocity is 6 m/s the total velocity is the vector sum of the horizontal and vertical components using Pythagoras, the vertical velocity must be 8 m/s ... it's a 3-4-5 triangle (6-8-10) B looks good
*July 5, 2016*

**Science**

(a) 7 N - 5 N = (b) the object displaced 2 N of water ... w = m g ... 2 = m * 9.8 ... the volume (in L) is equal to the mass of water (in kg) (c) the 7 N object has the same volume as 2 N of water ... its density is 7/2 water's density
*July 5, 2016*

**Physics**

μ > 85.0 / (30.0 * 9.80)
*July 4, 2016*

**math**

3000 + i = 3000 (1 + .07)⁸
*July 4, 2016*

**Physics**

m g μ = 50 N ... μ = 50 / (10 * 9.8)
*July 4, 2016*

**Physics**

momentum is mass times velocity velocity is ... Vi + (a * t) write their momenta in terms of t set the expressions equal, and solve for t
*July 4, 2016*

**Chemistry**

a mole of ANY gas occupies 22.4 L at STP the formula for ammonia (g) is NH₃ its molar mass is 17.0 g
*July 4, 2016*

**Pre Calculus**

the max is on the axis of symmetry of the parabola t = -b / 2a = -2100 / (2 * -80.6)
*July 4, 2016*

**Physical Science**

heat of fusion for ice ... 79.7 cal/g heat from iron ... 100 g * 72 ºC * 0.11 cal/g⋅ºC divide heat from iron by heat of fusion
*July 4, 2016*

**Math**

the volume of metal is ... v = 4/3 * π * (30³ - 20³) cm³ if the density units are g/cm³ then multiply v by .0078
*July 4, 2016*

**Math**

oops... k = 9 3k = 27
*July 4, 2016*

**Math**

2k + 3k + 5k = 3 * 30 cm 10k = 90 cm ... k = 10 cm a) 3 * k = 30 cm b) 90 cm + D = 4 * 33 cm ... D = 42 cm
*July 4, 2016*

**Physics**

(4 kg / 18 amu) * (1 amu / 1.7E-27 kg) careful of sig figs
*July 3, 2016*

**Physics**

emf - (internal resistance * current) = terminal voltage (Ri * .55) + 5.0 = (Ri * .18) + 5.7 emf - (1.9 * .55) = 5.0
*July 3, 2016*

**math**

x + (12½% x) = Rs. 500 1.125 x = Rs. 500
*July 2, 2016*

**physics**

h = ½ g t² ... t = √(2 * 12.0 / g) v = d / t = 7.35 m / t
*July 2, 2016*

**physics**

h = ½ g t² ... t = √(2 h / g) v = d / t = 13.5 m / t
*July 2, 2016*

**Chemistry**

the concentration is 10 Molar sample size is not a factor
*July 2, 2016*

**Chemistry**

(360 / 180) moles / .200 L = 10 M
*July 2, 2016*

**Physics**

it appears to be a format problem 1/60 = 1.67E-2 rev/s
*July 1, 2016*

**Physics**

it takes 60 s for one revolution so it must be 1/60 r/s
*July 1, 2016*

**physics**

1.6 lb / .62 lb/ft
*July 1, 2016*

**physics**

1. the distance is ... 15 km + 10 km 2. the displacement is a vector from their starting point to their finishing point use Pythagoras and trig to find the distance and direction
*July 1, 2016*

**Chemistry**

sulphuric acid is diprotic (2 H⁺) so the normality is twice the molarity
*July 1, 2016*

**chemistry**

one part 50% HCl to four parts H₂O
*July 1, 2016*

**math**

what question?
*July 1, 2016*

**Math(HELP PLEASE )**

given table?
*July 1, 2016*

**math**

the (2,½) is correct not the same as (2 , 2/1) there is only one solution
*July 1, 2016*

**physics**

0 = ½ g t² + v₀ t + h 0 = -4.9 * 6² + 24 * 6 + h
*June 30, 2016*

**Physics**

V = √(2 g h) momentum is conserved ... .2 * V = (.2 + .4) v
*June 29, 2016*

**Calculus**

v = x (16 - 2x)² solve for the volume take the 1st derivative (dv/dx), and set equal to zero solve for x test the two solutions
*June 29, 2016*

**Math2**

the distance below the mean of Bob's pumpkin (z-score) is ... (938.23 - 1029.51) / 674.29 use a z-score table to find if the value lies in the upper 55.17% of entries looks like he just missed...
*June 29, 2016*

**Math( Assignment Due Today)**

h / Da = tan(35º) Da / 42 m = tan(30º) h = 42 m * tan(35º) * tan(30º)
*June 29, 2016*

**Physics**

gravity is providing the centripetal force (keeping the satellite on a circular path) a = v² / r you have a and r, just make the units consistent (a to km OR r to m)
*June 29, 2016*

**Physics**

a = (30 - 20) km/h / 1.5 s t = (36 - 30) km/h / a
*June 29, 2016*

**Physics**

answered
*June 29, 2016*

**math**

(1 - .04) * 1000 = (.25 + .05) * t
*June 28, 2016*

**Physics**

the radius of the Earth is ... 6371 km g (at the surface) is ... 9.81 m/s² (a) using the inverse-square relation ... a / g = (7000/6371)² (b) the velocity of the satellite is ... v² / r = a ... v = √(a²/r) ... keep the units consistent by converting a...
*June 28, 2016*

**Chemistry**

there is one mole of NaCl and two moles of H₂O
*June 28, 2016*

**Admaths**

constant distance from a point is a circle, centered at the point x = k is a vertical line, tangent to the circle so the radius of the circle is k-1 (x - 1)² + (y - 2)² = (k - 1)²
*June 28, 2016*

**math**

the store buys the items for some cost (c), and then marks up the selling price to 140% of c (cost plus profit) the 10% price reduction means that the sale price is 126% of c (140 - 14) the cost (c) doesn't change, so the profit is reduced to 26% (126 - 100)
*June 28, 2016*

**math**

14 N is half of 28 N, so it must be placed twice as far from the fulcrum for equilibrium 8 * 28 = d * 14
*June 27, 2016*

**mathemarics**

A. (17,12) B. d = √(20² + 16²)
*June 27, 2016*

**geometry**

2.) (3,-½)
*June 27, 2016*

**geometry**

8 units apart in the x-direction 3 units apart in the y-direction d = √(8² + 3²)
*June 27, 2016*

**Math**

it takes 600 man-hr to reap the field 600 / (8 * 15)
*June 26, 2016*

**chemistry**

how many pairs of electrons can be put into these orbitals? s -- 1 p -- 3 d -- 5 a degenerate orbital can hold a pair of electrons
*June 26, 2016*

**math**

v(x) = x (8 - 2x)(5 - 2x)
*June 26, 2016*

**Probability**

there are 24C2 ways of selecting two movies there are 9C2 ways of selecting two Barney movies the probability is ... 9C2 / 24C2
*June 25, 2016*

**Physics**

ave. velocity = (20 + 0) / 2 = 10 m/s .04 m / 10 m/s = .004 s
*June 25, 2016*

**math**

1.2 b + .9 b = 2.1 b 2.1 b / 2 b = 1.05 1.05 - 1 = .05 = 5% profit
*June 25, 2016*

**math**

f , s , t .6 t , .5 t , t .6 t / .5 t = 1.2 = 120%
*June 25, 2016*

**Algebra**

m = 37 h - 1500
*June 25, 2016*

**Physics**

one charge is attracting and the other is repelling the 3rd charge must be farther from the larger charge and not between the two charges remember inverse square law 7.25 / (d + 20)² = 2.00 / d² 7.25 d² = 2 d² + 80 d + 800 5.25 d² - 80 d - 800 = 0 use ...
*June 24, 2016*

**Chemistry**

the molar mass of NaCl is ... 58.44 g the molar mass of KI is ... 166.00 g
*June 24, 2016*

**Probability**

it's a binomial expansion (r + t)¹⁰ ... you want the 8th term 10C7 [(40/75)³ (35/75)⁷]
*June 24, 2016*

**Science**

wavelength = velocity / frequency λ = 3.0E10 cm/s / 6.0E18 hz
*June 24, 2016*

**Physics**

the s.a. of a sphere is ... 4 π r² or ... π d² km² = 1E6 m²
*June 23, 2016*

**math**

6497 , 5579 , 5993
*June 23, 2016*

**Math**

1.11 x = 5173
*June 23, 2016*

**Physics**

(a) f = m a = .02/32 * 1E5 = 63 lb (b) yes ... Newton's 3rd Law ... equal and opposite reaction (c) .007 s * 1E5 ft/s² = 700 ft/s sounds like an air rifle
*June 22, 2016*

**Physics**

the longest wavelength (lowest energy) would be from the 2nd excited state to the 3rd excited state
*June 22, 2016*

**Physics**

the plane must fly northeasterly so that its north velocity component equals the south velocity component of the wind 250 sin(Θ) = 50 sin(45º)
*June 22, 2016*

**Math**

the height of the satellite and the line through the stations form the right angle of a right triangle there are two hypotenuses (hypoteni?), one from each of the stations to the satellite curious as to how you found A) without the height h / a = tan(87º) h / (a + 35) = ...
*June 22, 2016*

**Physics**

v² / r = g sin(2Θ) / 2
*June 22, 2016*

**Physics**

u - u/20 = 19u/20 = .95u .95² = .9025 the bullet loses about 10% of its energy (kinetic), as work passing through the plank it should stop in the 11th plank
*June 22, 2016*

**Algebra**

salary = 1800 + (sales * .042) 4824 = 1800 + .042 s 3024 = .042 s
*June 21, 2016*

**Physical Science**

(6.38E6)² / .89 = (6.38E6 + h)²
*June 21, 2016*

**Physical Science**

h = ½ g t² ... .3 = ½ * 9.8 * t² t = √(.6 / 9.8) distance = 3.1 * t
*June 21, 2016*

**Mathematics**

almost ... 12/4 = 3 ... not 8 (not an exponent)
*June 21, 2016*

**statistics**

this is a binary expansion (h + t)⁴ the term you want is...6 h² t² 6 * (2/3)² * (1/3)² = 24/81 = 8/27
*June 21, 2016*

**Physical Science**

F = G * (m₁ m₂) / r² F = 6.7E-11 * 4.8E24 / (6.4E6)² N
*June 21, 2016*

**Math1(Please Help Me)**

A.) about 99% of a normally distributed population lies within 2½ standard deviations of the mean 159 cm ± (2½ * 5 cm) 65.9 kg ± (2½ * 12.7 kg) B.) the weight seems more variable because the s.d. is a larger fraction of the mean C.) 7 cm ...
*June 21, 2016*

**physics**

d = r * t (80 * t/2) + (40 * t/2) = 60 120 t = 120 ... t = 1 r = d / t = 60 km / 1 hr = 60 km/hr
*June 21, 2016*

**Math1**

A.) the data is clustered around a central value (mean), with fewer data points towards the edges B.) from statistical software ... mean = 195.5 , s.d. = 18.33 231 lbs is 1.94 s.d. above the mean [(231 - 195.5) / 18.33] this represents 2.6% of the population .026 * 218 = 5.67...
*June 20, 2016*

**Math**

2x² + 5x - 52 = 0 (2x + 13) (x - 4) = 0 x = 4
*June 20, 2016*

**Chemistry**

you need 7 moles of HCl for a complete reaction 7 moles / .85 M/L =
*June 20, 2016*

**algebra**

x = 5 is correct
*June 20, 2016*

**Math (pre-celc 12)**

you are correct
*June 20, 2016*

**Please Help Me!**

A.) the data is clustered around a central value (mean), with fewer data points towards the edges B.) from statistical software ... mean = 195.5 , s.d. = 18.33 231 lbs is 1.94 s.d. above the mean [(231 - 195.5) / 18.33] this represents 2.6% of the population .026 * 218 = 5.67...
*June 20, 2016*

**math**

3.54E7 m / 3.00E8 m/s = 1.18E-1 s
*June 20, 2016*

**Math**

60º is 1/6 of the circle a = [π (7/2)²] / 6
*June 20, 2016*

**math**

angle?
*June 20, 2016*

**math**

answered
*June 20, 2016*

**math**

the area of an isosceles right triangle is one half the square of the hypotenuse a = 3² / 2
*June 20, 2016*

**Math**

w = 250 m / tan(50º)
*June 19, 2016*

**Maths**

adding 6 ... 2 < 2x < 18 dividing by 2 ... 1 < x < 9 integers greater than 1 and less than 9
*June 19, 2016*