Sunday

October 23, 2016
Total # Posts: 1,382

**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

*October 22, 2016*

**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

*October 21, 2016*

**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...

*October 21, 2016*

**algebra**

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

*October 21, 2016*

**math**

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

*October 21, 2016*

**science**

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

*October 21, 2016*

**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

*October 21, 2016*

**Math**

the one with the exponent between the two

*October 21, 2016*

**Math**

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

*October 21, 2016*

**math**

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

*October 20, 2016*

**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

*October 20, 2016*

**Precal**

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

*October 20, 2016*

**algebra**

200 (1 + .20)^3

*October 20, 2016*

**physics**

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

*October 20, 2016*

**Algebra**

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

*October 20, 2016*

**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

*October 19, 2016*

**physics**

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

*October 19, 2016*

**algebra**

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

*October 19, 2016*

**physics**

momentum is conserved the speed is zero

*October 19, 2016*

**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...

*October 19, 2016*

**math**

(1.05^7 - 1) * 100%

*October 19, 2016*

**math**

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

*October 19, 2016*

**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

*October 19, 2016*

**physics**

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

*October 19, 2016*

**physics**

60 = 1/2 k x^2 x = √(120 / 460)

*October 18, 2016*

**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

*October 18, 2016*

**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

*October 18, 2016*

**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

*October 18, 2016*

**Physics**

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

*October 18, 2016*

**algebra**

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

*October 18, 2016*

**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

*October 18, 2016*

**GENERAL PHYSICS**

100 * 2π / 60 / 2 sec

*October 18, 2016*

**math**

36 / 47 = x / 120

*October 18, 2016*

**Chemistry**

mole = 6.02E23 particles 5.43E24 / 6.02E23

*October 18, 2016*

**math help**

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

*October 18, 2016*

**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]

*October 18, 2016*

**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

*October 18, 2016*

**Physics**

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

*October 18, 2016*

**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

*October 17, 2016*

**Math**

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

*October 16, 2016*

**Math**

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

*October 16, 2016*

**phy 101**

momentum is conserved so they "trade" velocities

*October 16, 2016*

**Math**

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

*October 16, 2016*

**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

*October 16, 2016*

**Chemistry**

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

*October 15, 2016*

**Physical science**

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

*October 15, 2016*

**Math**

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

*October 15, 2016*

**Math 1105**

yes

*October 14, 2016*

**Physics**

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

*October 14, 2016*

**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

*October 14, 2016*

**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

*October 14, 2016*

**Physics**

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

*October 14, 2016*

**Math**

1:12::8:x

*October 13, 2016*

**chem**

(a) 0.5 * (20.00 / 25.0) * (250.0 / 25.0) (b) multiply the answer from (a) by the molar mass of HCl

*October 13, 2016*

**algebra**

a + b = 273 / 3 mph = 91 mph a - b = 7 mph adding equations (eliminating b) ... 2 a = 98 mph

*October 12, 2016*

**Physics**

the horizontal velocity is ... 31 m/s * cos(60º) the vertical velocity is ... 31 m/s * sin(60º) + ... 3.4 s * -9.8 m/s^2 add the two component vectors ... a^2 + b^2 = c^2

*October 12, 2016*

**problem solving**

s = m - 8 m - 6 = 3(s - 6) = 3 s - 18 m - 8 = 3 s - 20 susbstituting ... s = 3 s - 20 ... 20 = 2 s

*October 12, 2016*

**Physics**

height = 1/2 g t^2 + Vo t + Ho 0 = -4.90 * .750^2 + Vo * .750 + 4.80

*October 12, 2016*

**Physics**

the difference in total energy (kinetic plus potential) at the base and the top; is the energy input from the engine the ascent time is the average speed, (top + bottom) / 2; divided by the 4.40 km distance energy / time equals power your answer has 5 sig figs. but all the ...

*October 12, 2016*

**Physics**

energy = m g h = 73.0 * 9.81 * 420 time = 60 * 15 + 10 power = energy / time

*October 12, 2016*

**physics**

his weight plus the centripetal force must equal 1170 N 83.0 [g + (v^2 / r)] = 1170 v^2 / 18.0 = (1170 / 83.0) - 9.81

*October 10, 2016*

**physics**

pulling at an angle reduces the frictional force (by reducing the normal force) so the frictional force is ... .42 * {(85 * g) - [F sin(38º)]} the block is in equilibrium when the frictional force equals the horizontal component of the pulling force ... F cos(38º) ...

*October 10, 2016*

**Math**

(n / 3) - 7 = 0 n / 3 = 7 n = 7 * 3

*October 10, 2016*

**College Algebra**

y = a b^x 8 = a b^0 ... a = 8 2.4 = 8 b^1 ... .3 = b y = 8 * .3^x

*October 10, 2016*

**MATH**

division by zero is a no-no ... even 0/0 so the 2nd and 4th are undefined

*October 10, 2016*

**Algebra**

Q = 5 * 2^(S + 4)

*October 10, 2016*

**College Algebra**

5 * 1.083^13

*October 10, 2016*

**physics again**

the water velocity increase is due to the change in gravitational potential energy 1/2 m 3.00^2 - 1/2 m 2.07^2 = m g h 3.00^2 - 2.07^2 = 2 g h the kinetic energy of the jump is converted to gravitational potential energy 6.26^2 = 2 g h the max waterfall is the sum of the two ...

*October 9, 2016*

**physics**

the average speed over the interval is (3.00 m/s + 5.60 m/s) / 2 = 4.30 m/s 2/3 of its length is 1.00 m so the time of the interval is ... 1.00 m / 4.30 m/s the change in speed is ... 5.30 m/s - 3.00 m/s acceleration is ... speed change / time

*October 9, 2016*

**Physics**

dx = (14 t - 32) dt x = 7 t^2 - 32 t + c 25 = 7 (3^2) - 32 (3) + c 25 = 63 - 96 + c ... 58 = c x = 7 t^2 - 32 t + 58

*October 9, 2016*

**physics**

gravity is the centripetal force keeping the satellite in orbit g = m a = 76 kg * .63 m/s^2

*October 9, 2016*

**physics (super hard)**

the centripetal force at the top of the circle equals gravity v^2 / r = g v = √(g r)

*October 9, 2016*

**math**

a. v = 1/3 * pi * r^2 * h b. the base radius is 4 and the height is 3, so the slant height is 5 (3-4-5 triangle) the 5 is the radius of the circle of which the area of the cone is a segment ... the area of the circle is...25 pi the area of the cone is...4/5 * 25 pi

*October 9, 2016*

**math**

7 is the most likely outcome using distinguishable dice, there are 36 possible outcomes ... each of the six faces on a die can pair with the six faces on the other die ... 6 * 6 = 36 twelve of those outcomes result in a sum of 7 ... one third of the rolls

*October 9, 2016*

**Physics**

k = f / e k1 e1 = k2 e2 e2 / e1 = k1 / k2

*October 9, 2016*

**chemistry**

call the 2nd gas B 3 g of B is half as many moles as 2 g of A B / A = 3 / 1

*October 9, 2016*

**Jar Marbles**

a) one of the five red marbles has the number 3 on it, so the probability is 1/5 b) two marbles have the number 1 on them, one red and one blue ... so the probability is 1/2

*October 9, 2016*

**Maths**

u = 2t - 6 10u + t = 10t + u + 9 substituting ... 20t - 60 + t = 10t + 2t - 6 + 9 solve for t, then substitute back to find u

*October 8, 2016*

**physics**

gravitational force follows an inverse-square relationship inverse of 1/8 is 8 ... 8 squared is 64

*October 8, 2016*

**math**

The Holy Father sent a courier from Rome to Venice, commanding him that he should reach Venice in 7 days. The most illustrious Signoria of Venice also sent another courier to Rome, who should reach Rome in 9 days. And from Rome to Venice is 250 miles. It happened that by the ...

*October 7, 2016*

**Physics**

the average velocity during braking ... (13.1 + 0) / 2 divide the stopping distance by the average velocity to find the time

*October 4, 2016*

**Math**

take out a common factor

*October 4, 2016*

**Algebra**

common factor 5x (x + 2)

*October 4, 2016*

**Chemistry**

the reaction equation is written in MOLES 2 moles NO plus 1 mole O2 yields ... 2 moles NO2 so 5 moles of O2 uses 10 moles of NO find the molar (formula) weight of NO, and multiply by 10

*October 4, 2016*

**Physics**

the delay time is down and back ... twice the depth

*October 4, 2016*

**Physics**

how about 4 by 2.9 ...

*October 4, 2016*

**Physics**

time = √(2 * distance / acceleration) initial velocity = 2 (distance / time)

*October 4, 2016*

**Chemistry**

there are about 55.3 moles of water in a liter the mean (average) concentration of chloride ions will be twice the arithmetic average of the MgCl2 concentrations (two Cl- for each MgCl2) I would be tempted to disregard the 175 value as a "flier"...but that's up ...

*October 4, 2016*

**Science Check my work PLS**

#8 ... a range of 5 in the 3rd digit is fairly precise the accuracy is substantially flawed

*October 4, 2016*

**Science**

a = f / m = 3 / 1

*October 4, 2016*

**physics**

the period is related to the mass and the spring constant the amplitude is inconsequential

*October 4, 2016*

**physics**

momentum is conserved the 2nd (larger) piece moves in the opposite direction at 1/3 the speed

*October 4, 2016*

**physics**

P = m g h / t = 100 * 10 * 6 / 120 answer is in Watts

*October 4, 2016*

**Calculus II**

If f(x) - x cos (x), how many intervals would be needed to approximate with the Trapezoidal Rule with an error of E<.01?

*October 3, 2016*

**Math 115**

a million is a thousand thousand (276.5 / 3150.4) thousand per mi^2

*October 2, 2016*

**Physics**

Tn = d / 40 Ts = d / 60 Save = 2d / (5d / 120)

*October 2, 2016*

**Physics**

.6 g = v^2 / r

*October 2, 2016*

**Calculus**

f(x) = x^2 has a critical point (and a MINIMUM) at x=0 f(x) = (x^3 + 3x^2 - 4x - 12) / (x+2) ... has a critical point (and a "hole" at x=-2)

*October 2, 2016*

**College math**

p(white) = 9/24 = 3/8 p(green) = 8/24 = 1/3 p(w then g) = 3/8 * 1/3

*October 1, 2016*