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Posts by Scott

Total # Posts: 2,135

Chemistry
3 half-lives m * (1/2)^3 = 6

Chemistry
2 days (48 hr) is 8 half-lives 10.0 * (1/2)^8

Chemistry
5 / 20 = 1/4 = (1/2)^2 2 half-lives

Algebra 2
3 half-lives 345 * 1/2 * 1/2 * 1/2

Need help with math
people who own both (b) will be counted in both groups (laptop owners and desktop owners) when you count all of the households, the "both" group is only counted once 130 + 30 + 50 + b = 250

Mathematics
the area is side times altitude 30 * 15 = 25 * x

Math
8 oz per cup

Science
switching the electrical polarity also switches the magnetic polarity

Science 7
switching the wires changes the magnetic polarity of the coil

algebra 2
3000 = 2000 [1 + (.038 / 2)]^(2t) ... t is the number of years 1.5 = 1.019^(2t) log(1.5) = 2t * log(1.019)

Physics
the gravitational potential energy becomes work driving the pipe m g h = f d 450 * g * 1.5 = f * .45

Math
y^2 + 5y - 6 = y^2 - 5y + 6 + 8 5y + 5y = 6 + 8 + 6

Math
(x + 2)^2 - x^2 = 44 x^2 + 4x + 4 - x^2 = 44 4x + 4 = 44

Math
28x - 7y = -119 ... add to 1st eqn

math
draw a Venn diagram of three intersecting circles enclosed in a box label the circles S, F, and G S/F/G -- 2 ... these are in all the two way intersections S/F -- 10 + (2) S/G -- 4 + (2) F/G -- 6 + (2) S -- 19 + (2) + (10) + (4) F -- 13 + (2) + (10) + (6) G -- 10 + (2) + (4...

Math
A = 3M A - 3 = 4 (M - 3) = 4M - 12 3M = 4M - 9

Math
18 r^5 = 2/27 9 r^5 = 1/27 r^5 = 3^-3 / 3^2 = 3^-5

Math Grade 9
square rooting implies that the yard is square ... from the result of your answer, this is not the case the "perimeter" in this problem, is only three sides A = L * W = 50 P = L + 2W a good investigation might consist of a table comparing L, W, and P ... remember, ...

Algebra
p + r = 18 35p + 49r = 728 solve the system by substitution or elimination

math
10 is a factor ... ?????0 The hundred thousands and ten thousands digit are the same and are odd ... must be less than 3, and odd ... 11???0 The sum of the hundreds and the thousands digits is 10 ... neither one can be zero The tens digit is a cube number and is one more than ...

Physics
the blocks accelerate at ... 60/18 = 10/3 m/s^2 the force necessary for b ... 15 * 10/3

Science
you think right

College Calculus
the max height is on the axis of symmetry of the parabola ... t = -b / 2a ... -96 / (2 * -16) ... plug into the equation to find s velocity is ds/dt ... solve for t when s is zero ... plug into the 1st derivative of s(t)

math
24 / 5 m = 30 / x m 24 x = 150

Math/7th
3 / 2 = 14 / x 3x = 28 x = 28/3 = 9 min 20 sec

physics
900 watts is 900 joules per sec 5 min is 300 sec 900 * 300 = 270 kJ

Physics
the car goes through a quarter of a circle in 10 s, at a speed of 15 m/s so the circumference of the circle is ... 10 * 15 * 4 = 600 m ... the radius is ... 600 / 2π the centripetal force (which causes the car to travel in a curved path) is ... m v^2 / r when the car is ...

Science/Physics
n = c / (.612 c) = 1 / .612

algebra
p = 94 e^(.06 * 4)

Math
suppose that 8 of Maggie's hours coincided with Gina's 8 hours that would complete 1/3 (8/24) of the project Maggie then finishes the remaining 2/3 in 22 hours (30 - 8) so Maggie would take 33 hours alone ... she does 24/33 or 8/11 working 24 hours with Gina Gina does ...

math
3S + 10 = 2L 2S + 2L = 100 3S + 10 = 100 - 2S 5S = 90

math
S + L = 50

Physics
a = 75/360 * π * r^2 da/dt = 75/360 * π * 2r dr/dt da/dt = 75/360 * π * 2 * 6 * 0.3

math please help
42 / (r + 6) = 10 / r 42 r = 10r + 60

math please help
p = f + 8 310 / p = 270 / f ... 310 f = 270 p 310 f = 270 (f + 8) 310 f = 270 f + (8 * 270) 40 f = 8 * 270

physics
1/2 m v^2 = m g h v = √(2 * 9.8 * 1.2)

Math
looking at a polar cross section Monica's radius of rotation (r) is ... 3960 mi * sin(90 - 13) her speed is ... 2 * π * r / 24 hr

Math
one half of TWO fifths is ONE fifth 1/5 * 60 =

algbebra
cd = 1 / (5 - 2) = 1/3 t = f + 6 cd t = 2f + 3 = f + 2 ... 4th = -1 ... 1st = -1 - (3 * 1/3) = -2 ... 25th = -2 + (24 / 3) = 6 s = (-2 + 6) * (25/2)

algebra
f(x) = -1 (3x + 8)^2 the graph is tangent to the x-axis ... at (-8/3,0)

physics
v^2 = .20 m * 9.8 m/s^2 this is the tangential velocity (v) divide by the radius to find angular

Physics
two forces on the ball ... tension and gravity gravity equals the vertical component of tension centripetal force is the horizontal component m v^2 / [1.75 sin(78.0º)] = ... m g tan(78.0º)

Pure Math
(x + yi)^2 = x^2 + 2xyi - y^2 x^2 - y^2 = -5 x y = 6 i would suggest a graphical solution ... try fooplot u = 2 + 3i

physics
d = 1/2 * a * t^2

Maths GRE
TOTAL price ... 3200 + 1800 % options ... 1800 / (3200 + 1800) * 100%

Algebra
because of the absolute value ... 2x-8 = 18 ... AND ... 2x-8 = -18

Phyics
the centripetal force is ... 42/56 g v^2 / 250 m = 42/56 * 9.8 m/s^2 this is the tangential velocity if you want rpm, multiply by 60 (sec to min); and divide by the station circumference

math
d = 1/2 a t^2 = 1/2 * 2.14 * 1.79^2

physics
the mass is not a factor (8.5 * r)^2 / r = .89 g r = .89 g / (8.5^2)

Physics
momentum is conserved in both the x and y directions the initial momentum is all in the x direction -- the moving ball PMy = 3.0 m/s * sin(60º) * 1.2 kg BVy = PMy / 7.2 PMx = 3.0 m/s * cos(60º) * 1.2 kg BVx = 3.5 - (PMx / 7.2) use Pythagoras to find BV

Physics
M1V1 = M2V2 ... M1^2 V1^2 = M2^2 V2^2 5 M1 V1^2 = 4 M2 V2^2 5 M1^2 V1^2 / M1 = 4 M2^2 V2^2 / M2 5 / M1 = 4 / M2 M2 / M1 = 4 / 5

Precalc
Ac = c^2 / 4 π triangle perimeter = Pt = 100 - c At = [Pt / (2 + √2)]^2 / 2 ... = (Pt)^2 / (12 + 8√2) ... = (1E4 - 200 c + c^2) / (12 + 8√2) A = (c^2 / 4π) + ... [(1E4 - 200 c + c^2) / (12 + 8√2)] the minimum A lies on the axis of symmetry...

algebra
x y = 6 * 3 = 18 2 y = 18

math
divide 2nd by -2 ... x = 103 + 5y subtract 5y ... x - 5y = 103 they are the same line

science
the speed of sound in air is ... 375 yd/s (approx) the speed of light is relatively instantaneous 3 * 375 = ?

physics
a) 15.9 / g = 15.9 m/s / 9.8 m/s^2 c) time up equals time down ... twice a) e) time from c) times 18.0 m/s

Math
the one with the exponent between the two

Math
let a = 22 / kg, and b = 12 / kg a + b = 20 kg 22a + 12b = 15 * 20 12a + 12b = 240 10a = 60

math
b / 12 = 75 / b b^2 = 900

chemistry
the two reactants react in equal amounts to give two products in equal amounts let x = concentration of each product Kc = 0.85 = [x]^2 / [1.00 - x]^2 .85 - 1.7 x + .85 x^2 = x^2 .15 x^2 + 1.7 x - .85 = 0 use quadratic formula to find x moles = concentration * vessel size

Precal
10^-2 = 3x + 5 -4.99 = 3x

algebra
200 (1 + .20)^3

physics
the weight is not a factor 1/2 m v^2 = m g h v = √(7 g)

Algebra
3.3E10 = 4.069E6 (1 +.026)^y log(3.3E4 / 4.069) = y log(1.026)

Science
the volume of water is ... π * 12^2 * 3 m^3 a cubic meter (m^3) of water has a mass of 1000 kg (a metric ton) the weight is the mass multiplied by the gravitational acceleration ... g = 9.8 m/s^2 the weight is in Newtons -- a unit of force

physics
s.h. = 4186 4186 * 2 * 75 = 627900 rounding or sig fig?

algebra
3^3 * (a^2)^3 = 27 a^6

physics
momentum is conserved the speed is zero

physics
the mass is not a factor horizontal speed = Sh = S cos(54.5) the flight time to the basket is ... 10.4 m / Sh = 10.4 * cos(54.5) / S vertical speed = Sv = S sin(54.5) gravity slows the vertical speed to zero at the peak, halfway through the flight Sv / g = 1/2 * 10.4 / Sh S...

math
(1.05^7 - 1) * 100%

math
a. 4000 = A [1+(.104 / 365)^(11 * 365) b. 4000 = A e^(.104 * 11)

physics
a) after 1 s the vertical velocity is 2 m/s ... so the average velocity is 7 m/s for the 1st sec b) similar to a) ... the object reaches its peak after 1.2 s ... the average velocity is 6 m/s c) time up equals time down ... 1.2 + 1.2

physics
time up equals time down h = 1/2 g t^2 = 4.9 m/s^2 * (2 s)^2

physics
60 = 1/2 k x^2 x = √(120 / 460)

physics
1/2 k x^2 = 1/2 m v^2 k = m v^2 / 4.5^2 convert 60 km/hr to m/s and calculate

Arithmetic progression
10 is not correct ... the 10th term is 23 the difference between terms is 2 27 is (5 + 22) ... the 1st term plus 11 differences ... 27 is the 12th term

math
57 (60 - 3) are M, E, or ME ... E + M + ME = 57 ... E + M = 48 M + ME = 2 (E + ME) ... M + 9 = 2E + 18 ... M = 2E + 9 substituting ... E + 2E + 9 = 48 ... E = 13 (i) M + ME (ii) E + ME (iii) M (iv) E

Physics
he has a constant velocity (zero acceleration) so the net force on him is zero the frictional force must equal his weight

algebra
(4y + 1i)(4y - 1i)

Physics
if his last turn is to the south he will be 70 m S and 12 m W of his starting position use Pythagoras to find the displacement

GENERAL PHYSICS
100 * 2π / 60 / 2 sec

math
36 / 47 = x / 120

Chemistry
mole = 6.02E23 particles 5.43E24 / 6.02E23

math help
1/2 * b * h = 10 b = h + 1 substituting ... h^2 + h - 20 = 0 (h + 5)(h - 4) = 0 h - 4 = 0

Physics
A) 2 * 7 * 10 N to the left B) 2 * 1/2 * 10 * 7^2 J C) the PE from B is converted to KE ... v = √[2 * B / m]

math
a = 2 pt, b = 4 pt, c = 5 pt a + b + c = 28 2a + 4b + 5c = 100 a = 2c 2a + 2b + 2c = 56 ... substituting ... 3a + 2b = 56 4a + 8b + 10c = 200 ... substituting ... 9a + 8b = 200 subtract the equations (after multiplying) to eliminate b

Physics
a faster stop (because concrete is hard) means a greater impulse

physics
the ball's speed is being converted to gravitational potential energy 1/2 m 6.4^2 = ... m g (2.2 - 1.5) + 1/2 m v^2 6.4^2 = 1.4 g + v^2

Math
s + b + w = 42 s = 4b 3s + 2b + 1.5w = 102 substituting ... 5b + w = 42 ... 14b + 1.5w = 102

Math
2 ft^3 = 2 * 12 * 12 * 12 in^3 24 * 144 / 231

phy 101
momentum is conserved so they "trade" velocities

Math
64, 32, 16, 8, 4, 2, 1, 1/2

Physics
a. weight = mass * g b. normal force equals weight ... but in opposite direction c. Newton's 2nd law ... f = m a ... in this case ... a = f / m d. correct

Chemistry
molar mass of acetone ... 58.08 g moles of acetone ... 1.920 / 58.08 molar enthalpy is energy per mole

Physical science
(A) m g h = 15 m g (B) m g h = 1/2 m v^2 ... v = √(2 g h) = √(30 g)

Math
it takes 12 min (the LCM of the numbers) divide by their rates to find the number of laps

Math 1105
yes

Physics
there is no force in the horizontal direction (gravity is vertical), so the horizontal velocity remains constant

math
the longest side must be less than the sum of the two shorter side the difference between the longest and shortest sides must be less than the middle side L + A = 11 L < (A + 4) ... L < (11 - L + 4) ... 2 L < 15 ... L < 7.5 L = 7, A = 4

Physics
A) 18 m/s * 6 s B) 1/2 g t^2

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