# 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

(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?

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

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

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

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