Wednesday

January 18, 2017
Total # Posts: 1,628

**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*

**MATHS**

(120 / 2) √2 + 150

*June 17, 2016*

**math**

a) use fooplot dot com b) 4 ft c) set h=0 , then solve for t d) set h=30 , then solve for t ... two solutions e) never f) axis of sym ... 50 / (2 * 16) g) use value from f) in h(t)

*June 16, 2016*

**Please Help**

the smallest value for (X-5)² is zero so the range is any real number greater than or equal to 7

*June 15, 2016*

**Algebra**

they close the distance at 32 mph (128/4) x + x/3 = 4x / 3 = 32 mph

*June 15, 2016*

**Math**

they are separating at the rate of 125 mph s + s + 15 = 125 ... 2 s = 110

*June 15, 2016*

**college algebra**

no male non-smokers 17 smokers ... 5 female, 12 male 13 non-smokers, all female

*June 15, 2016*

**math**

3³ + 3 - (3/3)

*June 15, 2016*

**Physics**

his energy (gravitational) is ... m g (h+d) = 45 * 9.8 * (7+d) the depth (d) he reaches is based on the work done by the water ... w = f d = 1500 d 1500 d = 45 * 9.8 * (7+d) f = m a ... a = f / m his deceleration is the net force (gravity minus water) divided by his mass a...

*June 15, 2016*

**science**

two quarts is four pints (4 * 30%) + (3 * 20%) = (4 + 3) * x

*June 15, 2016*

**science**

her mass is the same -- 24 kg her weight is 1/6 of her weight on earth

*June 15, 2016*

**maths**

a) v = ⅓ π r² h = 16 π b) the radius of the circle is 5 cm ... √[(8/2)² + 3²] = 5 Θ = 2 π * 8 / 10

*June 15, 2016*

**Maths**

the ladder, wall, and ground form a Pythagorean triple (like 3-4-5) this one is 5-12-13

*June 13, 2016*

**Physics**

F = charge * velocity * field strength F = 2.76E-13 N

*June 13, 2016*

**Physics**

the normal force is equal to the gravitational force ... m g

*June 13, 2016*

**Maths**

12 pens out of 40 are neither red nor green a randomly selected pen has a 12/40 or .3 probability of being in this group not sure where 3/4 comes from...

*June 13, 2016*

**Algebra**

a negative number, multiplied an odd number of times, is still negative no real number, multiplied an even number of times, can be still negative pos times pos is pos neg times neg is pos

*June 13, 2016*

**Physics I (Classical)**

for b) and c), determine the force (Q) using the acceleration components and the components of (P) ... you have the mass of the block f = m a ... by components

*June 13, 2016*

**Engineering science**

distance up equals distance down time up equals time down 3.5 s to peak g = 9.8 m/s² average velocity = (3.5 * 9.8) / 2 total distance = (ave vel) * 7

*June 12, 2016*

**Chemistry**

12.5 mM HCl and 7.5 mM KOH after netralization ... 5.0 mM HCl in 75.0 mL of solution ... .067 M HCl pH = -log[H⁺] = -log[.067]

*June 12, 2016*

**Math**

the amount of flour needed is directly proportional to the number of cakes...more cakes, more flour the constant of proportionality (k) is the flour per cake 4⅗ * k = 2/3 dividing both sides by 4⅔ k = 10/69 lb/cake seems more like a cupcake...

*June 12, 2016*

**Science**

yes

*June 11, 2016*

**Physics**

work is ... force times distance you have both ... 125 N , 45 m

*June 11, 2016*

**Calculus**

a b = 2 ... a = 2 / b s = a + b = 2/b + b ds = db (-2/b² + 1) ds/db = -2/b² + 1 = 0 b = √2 s = 2√2

*June 10, 2016*

**Physics**

your analysis looks okay your problem might be too many significant figures in your result

*June 9, 2016*

**Biostatics**

15.9% of the fish have lengths more than 1 standard deviation below the mean

*June 8, 2016*

**Math**

diagram?

*June 8, 2016*

**Physics**

the force constants add in parallel 16 N/m

*June 8, 2016*

**Physics**

1)as the elevator accelerates upward, the student's weight increases f = m a ... w = m a = m (g + e) 2)the elevator decellerates to a stop, so the student's weight is less than normal...same equations as #1 3)the greater the CHANGE in weight, the greater the ...

*June 7, 2016*

**Physics**

constant force means constant acceleration the graph is a flat line (zero slope)

*June 7, 2016*

**Algebra**

f(x) = 4 x - x²

*June 7, 2016*

**mat**

3 n + 4 = 15 / n 3 n² + 4 n - 15 = 0 (3 n - 5) (n + 3) = 0 n = 5/3 ... or ... n = -3

*June 7, 2016*

**Science**

1000 mL * .25 M = x mL * .75 M

*June 7, 2016*

**Science**

sulfuric is a binary acid [.56 / (2 * .25)] * .030 M

*June 7, 2016*

**Physics**

GPE = m * g * h = .6 * 9.81 * .3 J KE = GPE v = √(2 g h) m/s

*June 7, 2016*

**Science ~ Astronomy**

not a ... we don't have the technology yet ... same for c b) ... computer modeling

*June 6, 2016*

**Statistics**

m - m ... 1/3 * 1/3 = 1/9 m - f ... 1/3 * 2/3 = 2/9 f - m ... 2/3 * 1/3 = 2/9 f - f ... 2/3 * 2/3 = 4/9 (i) 1/9 + 4/9 = 5/9 (ii) 2/9 + 2/9 = 4/9

*June 6, 2016*

**physics**

30 m/s / 1.5 m/s²

*June 6, 2016*

**science**

divide the mass of the zinc by its molar mass (65.4 g) to find the number of moles each mole of zinc will produce a mole of hydrogen gas (diatomic) multiply the moles by the molar mass of H₂ (2.02 g)

*June 5, 2016*

**chemistry**

44 g is one mole of propane so four moles of water are produced the molar mass of water is 18 g

*June 5, 2016*

**math,algebra**

L + C = 150 ... 75 L + 75 C = 150 * 75 40 L + 75 C = 7400 subtract the equations to eliminate C and solve for L

*June 5, 2016*

**Science**

find its mass (weigh it) then do like Archimedes and submerge the object to find its volume divide the mass by the volume

*June 5, 2016*

**MATH**

the radius, distance, and half the chord form a 5-12-13 triangle

*June 5, 2016*

**MATH**

the radius, half the chord, and the distance form a 3-4-5 triangle

*June 5, 2016*

**chemistry**

the sodium is the limiting reactant .6 moles

*June 5, 2016*

**Math**

[(76 - x) / 4]² + (x / 4)² = 205 76² - 152 x + x² + x² = 205 * 16 use the quadratic formula to find x either x or 76-x is shorter

*June 5, 2016*

**math**

s² < 6 s ... s < 6 any square with a side length less than 6

*June 5, 2016*

**Chemistry**

the estimated mass is to high (positive error) the amount is 10/240 ... A

*June 5, 2016*

**chemistry**

close ... D the decimal point makes the trailing zero significant

*June 5, 2016*

**Math**

when you connect the midpoints, the triangle formed is half the perimeter of the original triangle

*June 4, 2016*

**gen chem**

looking at the formula, there are two hydrogens for every carbon so ... 4.06x10^21 atoms of hydrogen there are 6 carbon atoms in each glucose molecule, so the number of molecules is ... 2.03x10^21 / 6

*June 4, 2016*

**Math - Year 10 - Simult. Equations**

o + t = 21 1 o + 2 t = 30 subtracting equations t = 9

*June 3, 2016*

**Maths - Year 10 - Simult. Equations**

50 f + 20 t = 310 f + t = 11 ... 20 f + 20 t = 220 subtracting equations (to eliminate t) 30 f = 90 ... f = 3 substitute back to find t

*June 3, 2016*

**math**

104² - 40² = x²

*June 3, 2016*

**advanced science**

net force is ... 1860 - 480 the acceleration is the net force divided by the mass significant figures appear to be a factor (Hint: there are two)

*June 3, 2016*

**advanced science**

the normal force is the force perpendicular to the load bearing surface...it is equal to the weight of the load on the surface in this case ... m * g the force is upward from the surface

*June 3, 2016*

**physics**

one

*June 3, 2016*

**Physics - Doppler Effect**

the frequency is lower, so the car is moving away from the listener 875/900 = (speed of sound) / ... (speed of sound + speed of car) they give you the temperature so that you can find the speed of sound (in air)

*June 2, 2016*

**chemistry**

.6 is correct ... due to H⁺ activity

*June 2, 2016*

**math**

law of cosines x² = 127² + 64² - [2 * 127 * 64 * cos(90º + 38º)]

*June 1, 2016*

**Physics**

answered yesterday

*June 1, 2016*

**Chemistry**

HCl totally dissociates, so the hydrogen ion concentration is .002 M pH = - log[H⁺] = - log(.002)

*June 1, 2016*

**Chemistry**

the volume increased by a factor of 2.5 the volume is directly proportional to the absolute (Kelvin) temperature ºK = ºC + 273

*May 31, 2016*

**math**

30 / 50 = 3 / 5

*May 31, 2016*

**Physics**

d = 1/2 a t²

*May 31, 2016*

**physics**

your distances from the speakers are different by a half wavelength (this is the reason for the sound "cancelling") 14 - 5 = 11 so the sound wavelength could be 22 ft

*May 31, 2016*

**Physics**

it takes ... 24 m/s / .65 m/s² to stop the average velocity is ... (24 + 0)/2 the stopping distance is the product of time and velocity

*May 31, 2016*

**Physics**

the component of the force that moves the crate (horizontal) is...the applied force, multiplied by the sine of the angle to the component 10N * sin(45º)

*May 31, 2016*

**chem**

the partial pressure is the total pressure, multiplied by the fraction of the gas involved in this case ...ppO = .32 * 132 atm ...ppN = (1 - .32) * 132 atm

*May 30, 2016*

**SCIENCE**

the 2nd one

*May 28, 2016*

**PHYSICS**

downward velocity at impact ... v = √(2 * 10 * 20) = 20 m/s upward velocity after impact ... v = √(2 * 10 * 15) = 10√3 m/s accel = Δv / t = (20 + 10√3) / .01 ...units are m/s²

*May 28, 2016*

**College algebra**

100 + 5 x = 103 + 4 x

*May 26, 2016*

**Algebra**

2.75 < 2.25 + (750 / p) < 3.75 .50 < 750 / p < 1.50 2 > p / 750 > 2/3 1500 > p > 500 none of the responses seem to be correct

*May 26, 2016*

**age problems(please help)**

S = 3s ... t = 5S = 15s t + 5 = 5(s + 5) = 5s + 25 3t + 15 = 15s + 75 substituting ... 3t + 15 = t + 75 solve for t

*May 25, 2016*

**Physical Science**

heat the ice to 0º melt the ice heat the water to 20º look up the heat of fusion for ice and the specific heats for ice and water

*May 25, 2016*

**physics**

the distance is closing, so the frequency is higher F = 50kHz * [1450 / (1450 m/s - 450 km/hr)]

*May 25, 2016*

**Calc-Math**

you need to use the product rule for xy x dy/dt + y dx/dt

*May 24, 2016*

**Physics**

its average speed while stopping is 30 mi/h there are 3600 sec in an hr , and 5280 ft in a mi d = 30 * 5280 * 6 / 3600 ... feet

*May 24, 2016*

**Math**

10 = 1/2 * g * t^2 20 / 9.8 = t^2

*May 24, 2016*

**math**

The area if a rectangle is x3y4. Which expression represents the length if the width is x2y

*May 24, 2016*

**physics**

C = Q / 100...100 C = Q capacitors add in parallel the charge is the same (redistributed) C + 10 = 100 C / 30 solve for C

*May 24, 2016*

**Math**

C. The answer is C, -7.

*May 24, 2016*

**Math**

It is impossible. 12, 14, or 16 may work, but I think you should give up on this equation...

*May 24, 2016*

**Gen Chem**

Thank you DrBob222!

*May 20, 2016*

**Gen Chem**

Knowing the MW of salicylic acid (138.12g/mol), design a procedure to make 100mL of a 0.0050M salicylic acid solution.

*May 20, 2016*

**General Chemistry**

That's why I was confused, it just states that the Fe(OH)3 has a solubility product of 10^-39. Any ideas?

*May 20, 2016*

**Organic Chemistry**

When I solve for Fe I get 1.75mL and for SYL I get 210mL. That can't be correct if we are trying to make 50mL. The equation is: Salicylic Acid + [Fe(H2o)6]^+3 ---> Iron-salicylate complex

*May 20, 2016*