Wednesday

July 30, 2014

July 30, 2014

Total # Posts: 28

**math**

what number is 66 2/3% of 81?

**Physics**

In a Joule experiment, a mass of 1.00 kg falls through a height of 50.0 m and rotates a paddle wheel that stirs 0.600 kg of water. The water is initially at 15 degrees C. By how much does its temperature rise (in degrees C)?

**physics**

A cylinder with a piston contains 0.3 kg of water at 100 degrees C. What is the change in internal energy of the water when it is converted to steam at 100 degrees C at a constant pressure of 1 atm? The density of water is 1000 kg/m^3 and that of steam is 0.6 kg/m^3. The laten...

**physics**

A flow calorimeter is used to measure the specific heat of a liquid. Heat is added at a known rate to a stream of the liquid as it passes through the calorimeter at a known rate. Then a measurement of the resulting temperature difference between the inflow and the outflow poin...

**7th grade math**

Oh my gosh, I'm dying of laughter. Jessie, why don't you stop being a little snot and pay attention in class. 26/143 = x/100 You cross-multiply 26*100=143*x 2600=143*x Then you find x, as Ms.Sue tried so nicely to explain to you, by dividing 2600 by 143 (2600/143) whic...

**algebra ll**

y = x^2 + 9x y = x*(x+9) at y = 0, x*(x+9)=0 This is only possible when x = 0 or -9.

**Chemistry**

Total is 100%, so assuming x is the fraction of Cu-63, (1-x) is the fraction of Cu-65. Atomic weight is the (weighted) average of all isotopes. Therefore you have: x*62.93 + (1-x)*64.93 = 63.55 x = 0.69. So you have 69% Cu-63 and 31% Cu-65.

**geometry**

The spacing got messed up... The first column is for P Second is for Q Third is for ~Q and the last is for P => ~Q

**geometry**

I'm assuming you're trying to say "if p, then not q". For this, the table should go like this: P Q ~Q P => ~Q T T F F T F T T F T F T F F T T

**math**

The slope between two points is: slope = (y2 - y1)/(x2 - x1) (0.6,0.5) = (x1,y1) and (0.2,-0.3) = (x2,y2). Plug in and solve for the slope.

**physics**

Frequency = (speed)/(wavelength) However! The speed of a wave is constant for a given medium (ex. air, water). Therefore doubling frequency halves the wavelength, but keeps speed constant.

**physics**

Same concept as for this question: "Doubling the frequency of a wave source doubles the speed of the waves"

**physics, please help me, this question is hard**

a. Vf^2 = Vi^2 + 2*a*d solve for Vi given Vf = 0 (speed at max height is 0), a = -9.81 m/s^2 and d = 3m. b. Once you know Vi, you can use Vf = a*t + Vi and solve for t. (once again, Vf = 0 since you're only considering the path of the ball from the top of the building to m...

**math**

The difference of cubes formula is: x^3 − y^3 = (x − y)*(x^2 + xy + y^2) Your x is x in this case and y = 8 (2^3). So you get: x^3 - 2^3 = (x - 2)*(x^2 + 2x + 4).

**Math**

A round pool implies the pool is a cylinder. The volume of a cylinder is: V = (pi)*r^2*h where r is radius and h is height. Rearranging the formula, you get: h = V/(pi*r^2) V = 48.2 and r = 3.2, so h = 1.5 feet.

**Math**

A cube with volume 216 has sides of length 6cm. The volume of a pyramid is (1/3)*A*h (where A is the area of the base and h is the height of the pyramid). Therefore, the volume is (1/3)*6*6*6 = 72 cm^3 (answer C).

**Math**

This can also be solved by doing: x-y = 88 min x*y. x = 88+y, so you get minimize x^2+88x, which can be done with calculus.

**Math**

-44 and 44.

**math**

(10 choose 4)*(14 choose 4) The general formula for n choose k is (n!)/(k!*(n-k)!).

**Alegebra 1**

If all the vertices of a triangle are on the circle and one side of the triangle is the diameter of the circle it is a right angle. Find the length of the diameter (AC) if Ab =8 and BC = 15.

**geometry**

If Jan takes exactly 30 minutes to walk to school each day, and her school is 2.3 miles away, what is her average walking speed (rounded to the nearest tenth)?

**physics**

The nine Ring Wraiths want to fly from Barad-Dur to Rivendell. Rivendell is directly north of Barad-Dur. The Dark Tower reports that the wind is coming from the west at 52 miles per hour. In order to travel in a straight line, the Ring Wraiths decide to head northwest. At what...

**math **

so is it (-3/4,-1/2)?

**math **

whats the vertex of 4y^2+4y-16x+13=0?

**biology**

its C i figured it out

**biology**

The structures in bryophytes that penetrate the ground and act like roots are a. xylem b. phloem c. rhizomes d. rhizoids

**math**

7 bats minimum all can see out of only 1 eye

**physics**

A train pulls away from a station with a constant acceleration of 0.44 m/s2. A passenger arrives at a point next to the track 6.2 s after the end of the train has passed the very same point. What is the slowest constant speed at which she can run and still catch the train?

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