# Posts by Scott

Total # Posts: 2,157

**physics**

it takes the 1st stone 2 s to reach its peak and return to the top of the tower, now going downward with the same velocity as the 2nd stone that velocity is 9.8 m/s when it reaches the ground, its velocity is 39.2 m/s...4 s * 9.8 m/s its average velocity is 24.5 m/s ... (9.8...

**science**

.001 moles / .5 L = .002 M

**science**

λ =330 m/s / 1E4 cycles/s = 33 mm

**physics**

the average speed is 10.0 m/s ... 70.0 m / 7.00 s 1st point speed is 5.00 m/s ... 10 = (15 + 5) / 2 acceleration is (10.0 m/s / 7.00 s)

**Science**

mass * [heat of vaporization + (specific heat * temp change)]

**Chemistry**

a mole of ANY gas occupies 22.4 L at stp (5.2 / 22.4) * Avogadro's number

**Algebra**

(3 / 2s) + (1 / s) = 1 / 9 27/2 + 9 = s = 45/2 b = 2/3 s = 15

**physics**

combined force is 2 kN each pier acts as a fulcrum in a class 2 lever system 6 m * 2 kn = 10 m * f1 4 m * 2 kn = 10 m * f2

**math**

f + s = 205 5 f + 15 s = 2025 ... f + 3 s = 405 subtracting equations ... 2 s = 200

**Physics**

1 / R + 1 / 400 = 5 / R 1 / 400 = 4 / R

**Chemistry**

a liter of solution has a mass of 1.114 kg 20.0% of that is H₃PO₄ ... 222.8 g the molar mass of H₃PO₄ is ... 97.99 g so the moles/L is ... 222.8 / 97.99 the 20.0 means 3 sig fig

**Math**

g(x) = -2 (2x - 4)³ - 1

**Math**

f(x) = (x + a) (x + b)² (x + c)³

**maths**

2 sin(21º) = cos(69º) sin(29º) = cos(61º) so it's twice sin² + cos²

**math,maths**

x/x + 2/x ≥ .2 1 + 2/x ≥ .2 2/x ≥ -.8 2 ≥ -.8 x -5/2 ≤ x

**Math**

the distance is the same 10 (s - 21) = 7 s 10 s - 210 = 7s

**math**

r + b = 365 ... 10 r + 10 b = 3650 9.5 r + 10 b = 3645 subtracting equations ... .5 r = 5

**Pre-Calculus 11**

squaring ... 9 - 6x + x² = x² - 5 x = 7/3

**math**

L = w + 5 w * (w + 5) = 500 w² + 5 w - 500 = 0 factoring ... (w + 25) (w - 20) = 0 w = 20 ... L = 25

**Physics**

heat = mass * temperature change * specific heat for the water heat = 200 g * 7.2 ºC * 1 cal/gºC heat gained by the water is the heat lost by the metal for metal heat = 95 g * 70.8 ºC * s.h. s.h. = (water heat) / (95 * 70.8) be aware of significant figures in ...

**Algebra**

ln(y) + 5 ln(y+1)

**physics**

each of the four sides of the square is 5 Ω diagonally, there are two parallel paths of two 5 Ω resistances in series each path is 10 Ω (5 + 5), and the two paths in parallel results in a net resistance of 5 Ω

**physics**

a hanging spring with a freely hanging mass the force (from gravity) is ... m * g = .98 N k = F / d = .98 N / .01 m = 98 N/m

**PHYSICS**

multiplying or dividing ...add the percent uncertainties 16 ± 2.25% the cm are cancelled in the division process...it's just a ratio

**Algebra**

squaring both sides ... 36 = n^(2x) multiplying by n ... 36 n = n^(2x + 1)

**Algebra**

the drop time is ... t = 132 ft/s / 32 ft/s² it starts from rest, so the average velocity is ... (0 + 132) / 2 ft/s the distance is ... d = drop time * average velocity

**Science**

going directly from a solid to a gas is called sublimation

**Physics**

heat = mass * temp change * specific heat make sure the units are consistent

**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]

**Chemistry**

the iron is oxidized the hydrogen is reduced

**Physics**

80 C / .001 s = 80000 C/s = 80 kA

**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

**Math**

-3 is not a root the roots are ... -3±i 4, -3+i, -3-i

**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 ...

**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

**Analytic geometry**

this is a line that is the perpendicular bisector of the line between the given points

**Analytic geometry**

this is an ellipse the two given points are the foci

**CHEMISTRY**

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

**Physics**

average velocity is ... (4 + 14) / 2 d = v t

**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

**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

**Physics**

μ > 85.0 / (30.0 * 9.80)

**math**

3000 + i = 3000 (1 + .07)⁸

**Physics**

m g μ = 50 N ... μ = 50 / (10 * 9.8)

**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

**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

**Pre Calculus**

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

**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

**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

**Math**

oops... k = 9 3k = 27

**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

**Physics**

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

**Physics**

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

**math**

x + (12½% x) = Rs. 500 1.125 x = Rs. 500

**physics**

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

**physics**

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

**Chemistry**

the concentration is 10 Molar sample size is not a factor

**Chemistry**

(360 / 180) moles / .200 L = 10 M

**Physics**

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

**Physics**

it takes 60 s for one revolution so it must be 1/60 r/s

**physics**

1.6 lb / .62 lb/ft

**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

**Chemistry**

sulphuric acid is diprotic (2 H⁺) so the normality is twice the molarity

**chemistry**

one part 50% HCl to four parts H₂O

**math**

what question?

**Math(HELP PLEASE )**

given table?

**math**

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

**physics**

0 = ½ g t² + v₀ t + h 0 = -4.9 * 6² + 24 * 6 + h

**Physics**

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

**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

**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...

**Math( Assignment Due Today)**

h / Da = tan(35º) Da / 42 m = tan(30º) h = 42 m * tan(35º) * tan(30º)

**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)

**Physics**

a = (30 - 20) km/h / 1.5 s t = (36 - 30) km/h / a

**Physics**

answered

**math**

(1 - .04) * 1000 = (.25 + .05) * t

**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...

**Chemistry**

there is one mole of NaCl and two moles of H₂O

**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

**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)

**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

**mathemarics**

A. (17,12) B. d = √(20² + 16²)

**geometry**

2.) (3,-½)

**geometry**

8 units apart in the x-direction 3 units apart in the y-direction d = √(8² + 3²)

**Math**

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

**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

**math**

v(x) = x (8 - 2x)(5 - 2x)

**Probability**

there are 24C2 ways of selecting two movies there are 9C2 ways of selecting two Barney movies the probability is ... 9C2 / 24C2

**Physics**

ave. velocity = (20 + 0) / 2 = 10 m/s .04 m / 10 m/s = .004 s

**math**

1.2 b + .9 b = 2.1 b 2.1 b / 2 b = 1.05 1.05 - 1 = .05 = 5% profit

**math**

f , s , t .6 t , .5 t , t .6 t / .5 t = 1.2 = 120%

**Algebra**

m = 37 h - 1500

**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 ...

**Chemistry**

the molar mass of NaCl is ... 58.44 g the molar mass of KI is ... 166.00 g

**Probability**

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

**Science**

wavelength = velocity / frequency λ = 3.0E10 cm/s / 6.0E18 hz

**Physics**

the s.a. of a sphere is ... 4 π r² or ... π d² km² = 1E6 m²

**math**

6497 , 5579 , 5993

**Math**

1.11 x = 5173

**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