Tuesday

January 17, 2017
Total # Posts: 1,615

**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

*July 5, 2016*

**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

*July 5, 2016*

**Physics**

μ > 85.0 / (30.0 * 9.80)

*July 4, 2016*

**math**

3000 + i = 3000 (1 + .07)⁸

*July 4, 2016*

**Physics**

m g μ = 50 N ... μ = 50 / (10 * 9.8)

*July 4, 2016*

**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

*July 4, 2016*

**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

*July 4, 2016*

**Pre Calculus**

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

*July 4, 2016*

**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

*July 4, 2016*

**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

*July 4, 2016*

**Math**

oops... k = 9 3k = 27

*July 4, 2016*

**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

*July 4, 2016*

**Physics**

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

*July 3, 2016*

**Physics**

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

*July 3, 2016*

**math**

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

*July 2, 2016*

**physics**

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

*July 2, 2016*

**physics**

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

*July 2, 2016*

**Chemistry**

the concentration is 10 Molar sample size is not a factor

*July 2, 2016*

**Chemistry**

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

*July 2, 2016*

**Physics**

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

*July 1, 2016*

**Physics**

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

*July 1, 2016*

**physics**

1.6 lb / .62 lb/ft

*July 1, 2016*

**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

*July 1, 2016*

**Chemistry**

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

*July 1, 2016*

**chemistry**

one part 50% HCl to four parts H₂O

*July 1, 2016*

**math**

what question?

*July 1, 2016*

**Math(HELP PLEASE )**

given table?

*July 1, 2016*

**math**

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

*July 1, 2016*

**physics**

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

*June 30, 2016*

**Physics**

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

*June 29, 2016*

**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

*June 29, 2016*

**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...

*June 29, 2016*

**Math( Assignment Due Today)**

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

*June 29, 2016*

**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)

*June 29, 2016*

**Physics**

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

*June 29, 2016*

**Physics**

answered

*June 29, 2016*

**math**

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

*June 28, 2016*

**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...

*June 28, 2016*

**Chemistry**

there is one mole of NaCl and two moles of H₂O

*June 28, 2016*

**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

*June 28, 2016*

**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)

*June 28, 2016*

**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

*June 27, 2016*

**mathemarics**

A. (17,12) B. d = √(20² + 16²)

*June 27, 2016*

**geometry**

2.) (3,-½)

*June 27, 2016*

**geometry**

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

*June 27, 2016*

**Math**

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

*June 26, 2016*

**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

*June 26, 2016*

**math**

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

*June 26, 2016*

**Probability**

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

*June 25, 2016*

**Physics**

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

*June 25, 2016*

**math**

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

*June 25, 2016*

**math**

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

*June 25, 2016*

**Algebra**

m = 37 h - 1500

*June 25, 2016*

**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 ...

*June 24, 2016*

**Chemistry**

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

*June 24, 2016*

**Probability**

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

*June 24, 2016*

**Science**

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

*June 24, 2016*

**Physics**

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

*June 23, 2016*

**math**

6497 , 5579 , 5993

*June 23, 2016*

**Math**

1.11 x = 5173

*June 23, 2016*

**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

*June 22, 2016*

**Physics**

the longest wavelength (lowest energy) would be from the 2nd excited state to the 3rd excited state

*June 22, 2016*

**Physics**

the plane must fly northeasterly so that its north velocity component equals the south velocity component of the wind 250 sin(Θ) = 50 sin(45º)

*June 22, 2016*

**Math**

the height of the satellite and the line through the stations form the right angle of a right triangle there are two hypotenuses (hypoteni?), one from each of the stations to the satellite curious as to how you found A) without the height h / a = tan(87º) h / (a + 35) = ...

*June 22, 2016*

**Physics**

v² / r = g sin(2Θ) / 2

*June 22, 2016*

**Physics**

u - u/20 = 19u/20 = .95u .95² = .9025 the bullet loses about 10% of its energy (kinetic), as work passing through the plank it should stop in the 11th plank

*June 22, 2016*

**Algebra**

salary = 1800 + (sales * .042) 4824 = 1800 + .042 s 3024 = .042 s

*June 21, 2016*

**Physical Science**

(6.38E6)² / .89 = (6.38E6 + h)²

*June 21, 2016*

**Physical Science**

h = ½ g t² ... .3 = ½ * 9.8 * t² t = √(.6 / 9.8) distance = 3.1 * t

*June 21, 2016*

**Mathematics**

almost ... 12/4 = 3 ... not 8 (not an exponent)

*June 21, 2016*

**statistics**

this is a binary expansion (h + t)⁴ the term you want is...6 h² t² 6 * (2/3)² * (1/3)² = 24/81 = 8/27

*June 21, 2016*

**Physical Science**

F = G * (m₁ m₂) / r² F = 6.7E-11 * 4.8E24 / (6.4E6)² N

*June 21, 2016*

**Math1(Please Help Me)**

A.) about 99% of a normally distributed population lies within 2½ standard deviations of the mean 159 cm ± (2½ * 5 cm) 65.9 kg ± (2½ * 12.7 kg) B.) the weight seems more variable because the s.d. is a larger fraction of the mean C.) 7 cm ...

*June 21, 2016*

**physics**

d = r * t (80 * t/2) + (40 * t/2) = 60 120 t = 120 ... t = 1 r = d / t = 60 km / 1 hr = 60 km/hr

*June 21, 2016*

**Math1**

A.) the data is clustered around a central value (mean), with fewer data points towards the edges B.) from statistical software ... mean = 195.5 , s.d. = 18.33 231 lbs is 1.94 s.d. above the mean [(231 - 195.5) / 18.33] this represents 2.6% of the population .026 * 218 = 5.67...

*June 20, 2016*

**Math**

2x² + 5x - 52 = 0 (2x + 13) (x - 4) = 0 x = 4

*June 20, 2016*

**Chemistry**

you need 7 moles of HCl for a complete reaction 7 moles / .85 M/L =

*June 20, 2016*

**algebra**

x = 5 is correct

*June 20, 2016*

**Math (pre-celc 12)**

you are correct

*June 20, 2016*

**Please Help Me!**

A.) the data is clustered around a central value (mean), with fewer data points towards the edges B.) from statistical software ... mean = 195.5 , s.d. = 18.33 231 lbs is 1.94 s.d. above the mean [(231 - 195.5) / 18.33] this represents 2.6% of the population .026 * 218 = 5.67...

*June 20, 2016*

**math**

3.54E7 m / 3.00E8 m/s = 1.18E-1 s

*June 20, 2016*

**Math**

60º is 1/6 of the circle a = [π (7/2)²] / 6

*June 20, 2016*

**math**

angle?

*June 20, 2016*

**math**

answered

*June 20, 2016*

**math**

the area of an isosceles right triangle is one half the square of the hypotenuse a = 3² / 2

*June 20, 2016*

**Math**

w = 250 m / tan(50º)

*June 19, 2016*

**Maths**

adding 6 ... 2 < 2x < 18 dividing by 2 ... 1 < x < 9 integers greater than 1 and less than 9

*June 19, 2016*

**Physical Science 8th Grade**

1. in a surface wave (like water); the water goes up and down, but the wave travels across (parallel to) the surface 2. energy is transferred 3. sound 4. c 5. parallel to (sound)

*June 19, 2016*

**Maths**

w = 250 m / tan(50º)

*June 19, 2016*

**Physics**

power is power...mechanical or electric...measured in Watts watt = Joule/s = volts * amps watt·sec = Joule kilowatt·hr = 3.6 MJ energy = energy

*June 19, 2016*

**math**

(59 - 3) / 4 = 14 14 + 1 = 15 terms

*June 19, 2016*

**Math**

z1 = 50 kg c2 = 150 kg t1 = 4/3 t2 4/3 t2 + t2 = 140 kg ... 7/3 t2 = 140 ... t2 = 60 kg ... t1 = 80 kg c1 = 200 kg - 50 kg - 80 kg = 70 kg c1 + c2 = 220 kg

*June 19, 2016*

**Math**

implicit differentiation 2 x dx/dt - 2 y dy/dt = 0 substituting [2*(-3)*(-4)] - [2*2*(dy/dt)] = 0

*June 18, 2016*

**Physics**

13 = -½ g t² + 24 t + 2 solve for t...there will be two solutions (up and down) the velocity is...v = 24 - g t ...use the up (smaller) time

*June 18, 2016*

**physic mechanic**

momentum is conserved .15 * 3.8 = 4.75 * v

*June 18, 2016*

**physical science**

momentum is conserved .16 * 25 = (85 + .16) * v

*June 17, 2016*

**Science : Physics**

balanced means zero net force Newton's 2nd law ... f = m * a if the force equals zero, then the acceleration also equals zero

*June 17, 2016*

**Geometry**

1 + 2 + 3 is a straight angle (180º) 3 is a right angle (90º) 1 + 2 = 90 = x + x - 6 = 2 x - 6

*June 17, 2016*

**Science : Physics**

the work done in stopping is... f * d ... 60 * 26.3 = ? J the work equals the initial kinetic energy of the object... ½ m v² 60 * 26.3 = ½ * 15 * v² v = √(8 * 26.3) m/s be aware of significant figures...

*June 17, 2016*

**Math**

1 + 2 + 3 is a straight angle (180º) 3 is a right angle (90º) 1 + 2 = 90 = x + x - 6 = 2 x - 6

*June 17, 2016*