# 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