Tuesday

October 13, 2015
Total # Posts: 589

**physics**

A person takes in a breath of 27C air and holds it until it warms to 36.5C. The air has an initial volume of 0.39 L and a mass of 0.00077 kg. Determine the work done by the air on the lungs if the pressure remains constant at 1 atm. Answer in units of J
*February 19, 2013*

**Math/Physics**

What is an expression for the standing wave that is produced by adding the two waves (2.5 cm)sin[(3.0 m-1)x - (27 s-1 )t] and (2.5 cm)sin[(3.0 m-1)x + (27 s-1)t]
*January 30, 2013*

**Physics**

Air is vibrating in a tube (closed at both ends) at its fundamental frequency of 160 Hz. If the tube is filled with helium instead, what is its fundamental frequency? Use 1020 m/s for the speed of sound in helium.
*January 30, 2013*

**Physics**

If the seventh and fourth standing wave frequencies of a string differ by 144 Hz, what is the fundamental frequency of the string?
*January 30, 2013*

**Physics**

Write an expression for the standing wave produced by adding the two waves (2.5 cm)sin[(3.0 m-1)x - (27 s-1 )t] and (2.5 cm)sin[(3.0 m-1)x + (27 s-1)t].
*January 30, 2013*

**Physics**

Two identical tuning forks have frequencies of 512 Hz. If one is held by a listener while the other approaches at a speed of 7.2 m/s, what does the listener hear?
*January 30, 2013*

**Physics**

the horizontal velocity of the ball is ___ Vh = 176 cos(35º) the vertical velocity of the ball is ___ Vv = 176 sin(35º) it takes the ball 565 / Vh seconds to reach the back wall the time to the peak of the ball's trajectory is ___ Vv / g the difference between ...
*January 18, 2013*

**Math**

x / (2x + 10) = 5 / 12 "cross" multiplying ___ 12x = 10x + 50
*January 18, 2013*

**Physics**

vacuum doesn't pull, pressure pushes b.
*January 18, 2013*

**Physics**

500 N/m^2 b.
*January 18, 2013*

**Physics**

2 s up and 2 s down the velocity took 2 s to drop to zero (at the peak of the flight) so it must have started at 20 m/s
*January 14, 2013*

**Chemistry**

calculate the pH of a 0.2moldm-3 solution of ammonia at 298K given that Kb for ammonia is 1.8x10-5
*January 6, 2013*

**Math**

It is not a school question. It is a real life question. So let's assume the interest averaged 4 % compounded daily over the 27 years.
*December 19, 2012*

**Math**

$2700 left in an account paying 4% interest would be worth how much today?
*December 19, 2012*

**Economics**

$2700 left in a variable rate interest bearing account in 1986 is worth how much today ?
*December 19, 2012*

**Math**

If I left $2700 in a variable rate interest account in 1986, how much is it worth today ?
*December 19, 2012*

**physics**

A block starts at rest and slides down a fric- tionless track. The acceleration of gravity is 9.81 m/s2 . It leaves the track horizontally, striking the ground (as shown in the figure above). b b b b b b b b b b b b 502 g h 2.2 m 4.4 m 9.81 m/s2 a) At what height h above the ...
*December 3, 2012*

**Physics**

Two banked curves on a highway have the same radius. Curve A is banked at 13 degrees and highway B is banked at 19 degrees. A car can travel around curve A without relying on friction at a speed of 18 m/s. At what speed can this car travel around curve B without relying on ...
*November 27, 2012*

**physics**

A flight attendant pulls her 74.2 N flight bag a distance of 324 m along a level airport floor at a constant velocity. The force she exerts is 37.9 N at an angle of 55.2 above the horizon- tal. a) Find the work she does on the flight bag. Answer in units of J 024 (part 2 ...
*November 22, 2012*

**physics**

A 42.1 kg diver steps off a diving board and drops straight down into the water. The water provides an average net force of resistance of 1559 N to the diver’s fall. If the diver comes to rest 4.1 m below the water’s surface, what is the total distance be- tween the ...
*November 22, 2012*

**physics**

Calculate the speed of an 7.6×104 kg airliner with a kinetic energy of 1.2 × 109 J. Answer in units of m/s
*November 22, 2012*

**Physics**

During a baseball game, a batter hits a pop up to a fielder 65m away. The acceleration of gravity is 9.8m/s^2. If the ball remains in the air for 5.7s, how high does it rise? Answer in units of m.
*November 19, 2012*

**physics**

Give up. Drop out of school
*November 16, 2012*

**physics**

65 = .5 g t^2 130 = 9.8 t^2 the distance is 7.8*t
*November 11, 2012*

**physics**

.4 = .5 g t^2 .8 = 9.8 t^2 the x-velocity is 76/t
*November 11, 2012*

**physics**

I got -29.43m\s but that's not taking air resistance Into consideration.
*November 7, 2012*

**physics**

A student moves a box of books down the hall by pulling on a rope attached to the box. The student pulls with a force of 173 N at an angle of 27.5 above the horizontal. The box has a mass of 27 kg, and μk between the box and the floor is 0.2. The acceleration of ...
*November 6, 2012*

**physics**

Consider the 57 N weight held by two cables shown below. The left-hand cable is horizon- tal. 57 N 52 a) What is the tension in the cable slanted at an angle of 52? Answer in units of N
*November 6, 2012*

**physics**

A 2.67 kg block starts from rest at the top of a 27.6 incline and accelerates uniformly down the incline, moving 2.89 m in 2.45 s. The acceleration of gravity is 9.81 m/s2 . a) What is the magnitude of the accelera- tion of the block? Answer in units of m/s2
*November 5, 2012*

**physics**

A 31 kg box slides down a 33.0 ramp with an acceleration of 1.30 m/s2. The acceleration of gravity is 9.81 m/s2 . Find the coefficient of kinetic friction between the box and the ramp.
*November 5, 2012*

**math(please help)**

Al + As + B = 124 Al + B = 102 subtracting equations ___ As = 22 Al + As = 86 subtracting equations ___ Al = 64 subtracting equations ___ B = 38
*November 4, 2012*

**Physics**

the vertical component of the brick's velocity is 13.9 * sin(27.6º) 0 = (-.5 g 3^2) + [13.9 * sin(27.6) * 3] + (building height)
*November 4, 2012*

**Math**

d/dx [cos(x)]^2 = 2 cos(x) * [-sin(x)]
*November 4, 2012*

**Pre- AP Physics**

the gravitational force between two objects is the same for both objects
*November 4, 2012*

**Math**

a. w = f * d = 150 * 4 = 600 Nm b. 600 / .5 = 1200 Nm
*November 3, 2012*

**physics**

A 1.6 kg otter starts from rest at the top of a muddy incline 95.9 cm long and slides down to the bottom in 0.50 s. What net external force acts on the otter along the incline? Answer in units of N
*November 3, 2012*

**physics**

A shopper in a supermarket pushes a loaded 32 kg cart with a horizontal force of 10 N. The acceleration of gravity is 9.81 m/s2 . a) Disregarding friction, how far will the cart move in 3.3 s, starting from rest?
*November 3, 2012*

**physics**

A freight train has a mass of 3.1 × 107 kg. If the locomotive can exert a constant pull of 4.9 × 105 N, how long would it take to increase the speed of the train from rest to 71.9 km/h? Disregard friction.
*November 3, 2012*

**physics**

f = m * a ___ a = f / m a = .052 N / 474 kg v = a * t ___ t = v / a t = 880 m/s / (.052 N / 474 kg) t will be in sec__convert to days
*October 30, 2012*

**physics**

Salmon often jump waterfalls to reach their breeding grounds. Starting 1.77 m from a waterfall 0.253 m in height, at what minimum speed must a salmon jumping at an angle of 44.8 leave the water to continue upstream? The acceleration due to gravity is 9.81 m/s2 . Answer in...
*October 16, 2012*

**physics**

A basketball player 1.9 m tall wants to make a basket from a distance of 7.8 m. The hoop is at a height of 3.05 m.If he shoots the ball (from a height of 1.9 m) at a 23.5 angle, at what initial speed must he shoot the basketball so that it goes through the hoop without ...
*October 16, 2012*

**math**

if an airplane is traveling at 245 meters per second, how many kilometers per second does it travel?
*October 10, 2012*

**Geometry**

interior + exterior = 180º
*October 3, 2012*

**7th grade Science help**

1. a 2. b 3. d
*September 26, 2012*

**math**

divide 1st (multiply by inverse) (1/3 * 7/5) + (5/14 * 7/5) 7/15 + 1/2 = 14/30 + 15/30
*September 26, 2012*

**Pre-Calculus**

f(x) + g(x) = (x^2) + (3x + 9) = x^2 + 3x + 9 = h(x) you can break it into whatever pieces you like h(x) = (x + 5)(x + 3) = x^2 + 8x + 15 f(x) = x^2 + 9 ; g(x) = 8x + 6 h(x) = f(x) + g(x) a. f(x) = 3x - 1 ; g(x) = 3 - 2x __ (3x - 1) + (3 - 2x) = x + 2 = h(x) b. f(x) = 7x - 3...
*September 26, 2012*

**physics**

it takes 5 s to stop the car __ 55 / 11 the average speed (Va) is __ (55 + 0) / 2 the stopping distance is __ Va * 5 twice as fast means that the stopping time is doubled, along with the average speed __ this means that the car travels 4 times as far
*September 26, 2012*

**math**

(3 1/2) / (2 1/3) (7/2) / (7/3) = 3/2 = 1 1/2
*September 26, 2012*

**science**

1. a 2. d 3. a 4. c 5. b
*September 26, 2012*

**science**

LARGER
*September 26, 2012*

**Physical Science**

you need 500 N to overcome the static friction as is frequently the case; once something starts, it is easier to keep it moving
*September 26, 2012*

**physics**

the frictional force is __ .29 g the time to stop is __ 5.6 / (.29 g) the average velocity is __ (5.6 + 0) / 2 the distance traveled is the average velocity divided by the time
*September 26, 2012*

**Physics**

t * 2.3 * 120 = (59/60) * 16 * 240
*September 26, 2012*

**math grade 10**

cuberoot(1280) cuberoot(64 * 20) 4 * cuberoot(20)
*September 26, 2012*

**Geometry**

if you double the length, you double the area to have an area of 55 and a perimeter of 32, the original garden was 5 X 11 so the increase in perimeter is 22 __ the percentage is __ (22/32) * 100
*September 26, 2012*

**Physics**

average speed (Va) is __ (23 + 0) / 2 time (t) is distance/speed __ 210 / Va acceleration is speed change/time __ (0 - 23) / t
*September 26, 2012*

**Stats**

74.2 * 85
*September 26, 2012*

**Chemistry**

if you over titrate, you should be able to correct with a titration of a standard acid if you think you may have added too much, the amount of the unknown acid will appear to be more than it actually is __ this would cause you to think you have more moles, so the equivalent ...
*September 26, 2012*

**chemistry**

1000 nm in a µm
*September 26, 2012*

**chemistry**

50C is halfway between the freezing and boiling points of water (0C and 100C) 50F is is slightly above the freezing point (32F) and well below the boiling point (212F)
*September 26, 2012*

**physics**

momentum is conserved 41 * 7 = v * (41 + 30)
*September 26, 2012*

**Physics**

the throwing angle has no effect the KE at impact is the initial KE plus the KE gained from the gravitational potential (m g h) KE = (.5 * .058 * 11.0^2) + (.058 * 9.8 * 12.3) v^2 = (2 * KE) / .058
*September 26, 2012*

**Chem**

the molecular weight of CS2 is 76.13 so the C in 67.1 g is: 67.1 * (12.01 / 76.13) the molecular weight of CCl4 is 153.81 so the C in 45.2 g is: 45.2 * (12.01 / 153.81) divide the CCl4 carbon by the CS2 carbon to find the percent yield
*September 26, 2012*

**Physics**

the frictional force (which must be overcome) is __ m * g * 0.200
*September 26, 2012*

**Physic**

(m v^2) / r = m g sinΘ v^2 = 6.00 m * g * sin(9.0º)
*September 26, 2012*

**Physics**

[2.00 * sin(37.0º)] + [1.785 * sin(153.5º)]
*September 26, 2012*

**Math**

look at 1000 items M1 produces 300 with 18 defects M2 produces 300 with 15 defects M3 produces 400 with 16 defects the probability that a defect is from M1: 18 / (18 + 15 + 16)
*September 26, 2012*

**statistics**

80 ≤ [(88 + 83 + 86 + 72 + 3x) / 7] ≤ 89
*September 26, 2012*

**Physics**

the centripetal force (gravity) is now 4 times as large f = m v^2 / r multiplying f by 4 (and keeping m and r constant) means that v is doubled doubling the velocity would halve the period
*September 26, 2012*

**Calculus-math**

using slope-intercept, the given slope is -1/2 the slope of the tangent to the function is the 1st derivative f(x) = 1 / sqrt(x) = x^(-1/2) f'(x) = (-1/2) x^(-3/2) substitute to find x and then y at the point of tangency use point-slope to write the equation of the new ...
*September 26, 2012*

**math**

16! / (7! * 1! * 8!)
*September 26, 2012*

**Physics**

the average velocity during deceleration is __ (76 km/h + 0) / 2 the time is the distance divided by the average velocity you will have to convert km/h to m/s to find the answer in s
*September 25, 2012*

**Physics**

the average velocity (Va) during acceleration is __ 3000 m / (3.8 * 60) sec the final velocity (Vf) is related to the initial velocity (Vi) by: Vf = (2 * Va) - Vi
*September 25, 2012*

**statistics**

there are 10C3 ways of drawing 3 chips there are 7C3 ways of drawing 3 red chips there is one way to draw 3 blue chips p = 1 - [(7C3 + 1) / 10C3]
*September 25, 2012*

**math**

(8 * 6) + (½ * 5 * 4)
*September 25, 2012*

**math**

-8bc^4
*September 25, 2012*

**Precalc**

you seem to be finding the axis of symmetry okay when you plugged in to find the vertex in #1, there is an error (should be 2,-4) __ this also affects the range completing the square should be: f(x) = (x - 2)^2 - 4 (x - 2)^2 = x^2 - 4x + 4 so you need to subtract out the extra...
*September 25, 2012*

**physics**

gravity also opposes the motion with a force of __ g * 297 * sin(25.9º) sum the forces; then find the acceleration with __ f = m a
*September 25, 2012*

**physics**

h = -.5 g t^2 + 2.6 t + 1.3 the max height occurs at the value of t that lies on the axis of symmetry (t = -b / 2a) __ t = -2.6 / -9.8 find t and substitute back to find the max height
*September 25, 2012*

**math**

Py = Pz = (2 * 5) + ( 2 * 3) write the equation for the perimeter of y using the length and width (2 * Ly) + (2 * Wy) = Py = Pz write the equation for the area of y using the length and width Ly * Wy = Ay = Py = Pz you now have two equations with two unknowns that you can ...
*September 25, 2012*

**algebra**

subtract the two equations to ELIMINATE the x-term -5y = 9 __ y = -9/5 substitute back to find x 4x + 9/5 = 5
*September 25, 2012*

**science**

gas equation temperatures are in Kelvin (absolute) v = (100 cm^3)[(1 atm) / (2 atm)](263º / 293º)
*September 25, 2012*

**physics**

it appears that the mass of the block is not involved in your final calculation (it cancels out in the second line) your work seems to be correct
*September 25, 2012*

**Physics**

you seem to have forgotten gravity add g to your acceleration number and you should be okay
*September 25, 2012*

**physics**

the acceleration is the change in velocity over time in this case __ (12.0 - 7) / 2.0
*September 25, 2012*

**Math**

Yoko's speed is 9/10 of Yolanda's in the time it takes Yolanda to run 110 yd, Yoko runs 99 yd so Yolanda wins the second race by a yard for a tie, the 100 yd that Yoko runs must be 9/10 of the distance that Yolanda runs .9 x = 100 __ x = 1000/9 Yoko runs 100 yd (900/9...
*September 24, 2012*

**math 176**

(x - 3y + 2z)(x - 3y - 2z)
*September 24, 2012*

**MaTh**

the area of the base is a factor of 42 with a perimeter of 18, the possible block arrangements are __ 8 X 1 __ area 8 7 X 2 __ area 14 6 X 3 __ area 18 5 X 4 __ area 20 14 is the only factor of 42, so the height must be 3
*September 24, 2012*

**Pre-Ap Physics**

the initial vertical velocity is __ (2650 m/s) * cos(41.9º) the time of flight is the initial vertical velocity divided by the gravitational acceleration __ 2 * [(2650 m/s) * sin(41.9º)] / (9.8 m/s^2) the horizontal velocity is __ (2.65 km/s) * cos(41.9º) the ...
*September 24, 2012*

**Science chemistry**

if n is the number of half-lives (1/2)^n * 1.000 = 0.121 (1/2)^n = 0.121/1.000 n [log(1/2)] = log(0.121) n = [log(0.121)] / [log(1/2)] half life = [1h17m] / n
*September 24, 2012*

**chem**

both compounds have one Cu, so the moles should be the same to find grams, multiply by the molar mass of CuO
*September 24, 2012*

**chemistry**

density is measured in g/cm^3 d = 19.07 / (3.1 * 1.9 * 4.6)
*September 24, 2012*

**Physics(Please help, thank you)**

the force that was needed to balance out F1 and F2 is equal in magnitude to the resultant, but opposite in direction so the resultant would be 280g at 77º since F1 and F2 have equal magnitudes and are 90º apart; the expected resultant would be 283g at 75º __ so ...
*September 24, 2012*

**physics**

momentum is conserved the mass of the clay, times its velocity; is equal to the mass of the clay+block, times its velocity 0.5 * v = (6 + 0.5) * 3
*September 23, 2012*

**Physics**

at 4s, the speed is 24 + 4g at 5s, the speed is 24 + 5g so the average speed over the interval (for one second) is 24 + 4.5g the distance is the speed times the time
*September 23, 2012*

**Physics**

h = .5 * g * t^2 34 = .5 * 9.8 * t^2
*September 23, 2012*

**physics**

constant velocity means no acceleration, which means zero net force so the third force is equal in magnitude to the resultant of the given forces; but opposite in direction the magnitude of the resultant of the given forces is __ sqrt(61.9^2 + 52.0^2) the tangent of the angle ...
*September 23, 2012*

**physics**

the work done on the car is reflected by the change in kinetic energy w = [.5 * 2000 * 20^2] - [.5 * 2000 * 10^2] the units are joules
*September 21, 2012*

**Science**

the kinetic energy at the bottom is the kinetic energy at the top plus the gravitational potential across the circle .5 m (Vb)^2 = [.5 m (Vt)^2] + [m g h] dividing by .5 m (Vb)^2 = (Vt)^2 + 2 g h v^2 = 3^2 + [2 * 9.8 * (2 * .8)]
*September 21, 2012*

**precal help**

n = d - 4 [(d - 4) / d] + [d / (d - 4)] = 5/2 multiplying by [2 * d * (d - 4)] [2 (d - 4)^2] + (2 d^2) = 5 d (d - 4) 2d^2 - 16d + 32 + 2d^2 = 5d^2 - 20d 0 = d^2 - 4d - 32 factoring __ 0 = (d - 8)(d + 4) 0 = d - 8 __ 8 = d
*September 21, 2012*