Saturday
February 13, 2016

# Posts by David

Total # Posts: 1,935

Chemistry
Carbon-14 has a half-life of 5730 y. How much of a 144 g sample of a carbon-14 will remain after 1.719 (times) 10 4y?
December 11, 2012

Chemistry
Dr. Bob, I don't need ur criticism now!! I need your help to resolve these problems
December 11, 2012

Math 10-3
the work i got from my math teacher says Determine the surface area of each right rectangular prism to the nearest square unit. Any Help with that?....
December 7, 2012

math
In 2 minutes, a conveyor belt moves 300 pounds of recyclable aluminum from the delivery truck to a storage area. A smaller belt moves the same quantity of cans the same distance in 6 minutes. If both belts are used, find how long it takes to move the cans to the storage area.
December 4, 2012

math
Three times the reciprocal of a number equals 9 times the reciprocal of 6. Find the number.
December 4, 2012

lenguage arts
examples of similes
December 3, 2012

Math
December 1, 2012

ACCOUNTING
Mills Company uses standard costing for direct materials and direct labor. Management would like to use standard costing for variable and fixed overhead. The following monthly cost functions were developed for manufacturing overhead items: Overhead Item Cost Function Indirect ...
December 1, 2012

math
Please, help me! 5/(x^2 - 4) + 2/(x^2 - 4x - 3) - 3/(x^2 - x - 6)
November 29, 2012

math
November 28, 2012

math
denaminator* (LCD)
November 28, 2012

math
Yes,I need to simplify it and find least common denamotator.
November 28, 2012

math
5/x^2-4+2/x^2-4x+4-3/x^2-x-6
November 28, 2012

Help ASAP calculus
Which is the 7th term in the sequence of the squares of all odd numbers starting from 1? 144 169 196 200 225
November 28, 2012

Urgent help calculus
If the area in square units of the region under the curve of the function f(x)=5, on the interval from x=a to x=8 is 20 square units what is the value of a? 4 5 6 7 8
November 28, 2012

Math
6y + 5x = -15. Find three solutions of the equation
November 22, 2012

chemistry
The pressure in car tires is often measured in pounds per square inch (), with the recommended pressure being in the range of 25 to 45 . Suppose a tire has a pressure of 33.5 . Convert 33.5 to its equivalent in atmospheres.
November 20, 2012

chemistry
The pressure in car tires is often measured in pounds per square inch (), with the recommended pressure being in the range of 25 to 45 . Suppose a tire has a pressure of 37.0 . Convert 37.0 to its equivalent in atmospheres.
November 20, 2012

Maths
3. Ohm’s law states that the current flowing in a circuit varies directly as the applied voltage and inversely as the resistance. In an experiment, the resistance was increased by triple the percentage by which the voltage was increased. A student calculated the percent ...
November 17, 2012

math
A chemist has 30%, 40 % and 80 % acid solutions. All three were to be mixed to make 4.00 x 102 L of 38% acid solution but a mistake was made and the amounts of 30% and 80 % were reversed. The result was 4.00 X 102 L of 65 % acid solution. What were the amounts of each solution...
November 17, 2012

Mathematics
There will be 12 cubes with paint on exactly two faces. There will be 27 smaller cubes in total, 9 on the 'top', 9 in the 'middle' and 9 on the 'bottom. The top and bottom are equivalent. Consider the top 9 cubes. The cube in the center only has one painted...
November 15, 2012

Physics
A stone is thrown from the ground with initial velocity v0 directed at angle alpha with respect to the horizon. Find equations of its motion both in x and y directions.
November 10, 2012

maths
3.An 1145 L tank contains 295 L of water and is being filled with brine from a full 1280 L tank at a rate of 1.55 U.S. gallons every 6 seconds. Will the smaller tank ever contain three times the amount of liquid as the larger tank? If so, when? If not, explain why.
November 4, 2012

maths
2. A bar of uniform section is 81.4cm long and weighs 4.45 kg. A weight of 12.8 kg is suspended from one end. The bar weight combination is to be suspended from a cable attached at the balance point. a)Determine how far from the weight should the cable be attached. b)Calculate...
November 4, 2012

maths
A large canal will have a cross-section in the shape of an isosceles trapezoid. The top will be twice as wide as the bottom, and the depth will be 8.00 m. Because of the cost of the building materials, the bottom and two slopes sides are to measure 14.0 m altogether. What is ...
November 4, 2012

math
how many ounces of liquid can be contained in a glass jar that is 5" tall and 3" in diameter (1 gallon =231 cubic inches)
November 4, 2012

CHEM!
A gas mixture contains 0.60 mol of N2, 0.10 mol of H2, 0.20 mol of CH4. Calculate the pressure of the gas mixture and the partial pressure of each constituent gas if the mixture is in a 6.0 L vessel at 27C. What is the: Total pressure Pressure of H2 Pressure of N2 Pressure of ...
October 29, 2012

Physics
The particles in the figure below (m1=1.6 kg and m2=3.5 kg) undergo an elastic collision in one dimension. Their velocities before the collision are v1i=12 m/s and v2i=-7.5 m/s. Find the velocities of the two particles after the collision. (Indicate the direction with the sign...
October 27, 2012

Physics
A railroad car (m=3000 kg) is coasting along a level track with an initial speed of 22 m/s. A load of coal is then dropped into the car as sketched in the figure below. (a) What are the velocities of the car and the coal before the collision along the x direction? Vcar=____m/s...
October 27, 2012

Finance
x = 33.96
October 24, 2012

MATH - ALGEBRA
October 22, 2012

math
it is not less than 40. it is not greater than 70. it is not an odd number. it does not have an even number in the tens place. it does not have a 4 in the ones place. it does not have a 6 in the ones place. what is the mystery number?
October 18, 2012

math
i have 8 coins in my piggy bank. I have twice as many dimes as I have quarters. I have twice as many pennies as I have dimes. I have less than 95 cents altogether. How many of each coin do I have?
October 17, 2012

marketing
explain how the e-business's online service fits within the e-marketing mix
October 15, 2012

math
This is the Crailsheim water tower in Baden-Württemberg, Germany. Its construction was completed in 1912. The base of the tower is a graduated cylinder about 19.2 m high with a diameter of 11.5 m at the base and 8.1 m at the top. a)The spherical tank holds 4.08  ...
October 10, 2012

math
A regular triangular pyramid has an altitude of 15.0 m and the base is 8.00 m on a side. Find the area of a section made by a plane parallel to the base and 8.00 m from the vertex.
October 10, 2012

maths
A chemical engineer designed a 625 ft long tailings channel to have a rhombus cross-section that is 9.5 ft deep, with walls sloping at an acute angle of 44„a. A contractor placed a bid to excavate the canal at \$195/cubic yard plus 20% profit. What was the bid?
October 10, 2012

physics
A pelican ﬂying along a horizontal path drops a ﬁsh from a height of 6.0 m. The ﬁsh travels 7.7 m horizontally before it hits the water below. What was the pelican’s initial speed? The acceleration of gravity is 9.81 m/s 2. If the pelican was ...
October 9, 2012

physics
Janet jumps oﬀ a high diving platform with a horizontal velocity of 2.25 m/s and lands in the water 1.6 s later. How high is the platform? The acceleration of gravity is 9.8 m/s 2
October 4, 2012

f(x,y,z)=xyz & 2xy+2xz+2yz=1300 & 4x+4y+4z=200 FIRST, simplify constraints: g(x,y,z)=xy+yz+xz=650 h(x,y,z)=x+y+z=50 THEN, take gradient vectors: for ▽f=<yz, xz, xy>=λ▽g+μ▽h =<λ(y+z), λ(x+z), λ(x+y)>+<μ, μ, &#...
October 4, 2012

calculus
If a rock is thrown upward on the planet Mars with a velocity of 13 m/s, its height in meters t seconds later is given by y = 13t − 1.86t2. (Round your answers to two decimal places.) (a) Find the average velocity over the given time intervals.
October 1, 2012

Physics
How do you find the v^2?
September 30, 2012

Physics
A mass m1 = 3.3 kg rests on a frictionless table and connected by a massless string over a massless pulley to another mass m2 = 4.4 kg which hangs freely from the string. When released, the hanging mass falls a distance d = 0.87 m. 1) How much work is done by gravity on the ...
September 30, 2012

math
Yes, they are relatively prime. 754 has factrs of 2, 13, and 29. 9471 has factors of 3, 7, 11, and 41
September 30, 2012

math
Four boxes of cereal are to be selected at random from a continuous process that fills boxes labeled "Contents: 340 g." The contents of the first three boxes are found to weigh 339.0g, 337.7 g, and 338.9 g. (a) What minimum weight of cereal must the fourth box ...
September 23, 2012

physics
Before going into orbit, an astronaut has a mass of 55 kg. When in orbit, a measurement determines that a force of 67.1 N causes her to move with an acceleration of 1.1 m/s2. To regain her original weight, should she go on a diet or start eating more candy? To answer this, ...
September 23, 2012

physics
The net external force on a golf cart is 398.2 N north. If the cart has a total mass of 274.1 kg, what is the cart’s acceleration? Answer in units of m/s2
September 23, 2012

physics
The net external force on the propeller of a 3.6 kg model airplane is 8.4 N forward. What is the acceleration of the airplane? Answer in units of m/s2
September 23, 2012

Physics
A ball is thrown from a point 1.38 m above the ground. The initial velocity is 19.9 m/s at an angle of 33.8° above the horizontal. Find the maximum height of the ball above the ground. Calculate the speed of the ball at the highest point in the trajectory.
September 22, 2012

statistics
The director of an alumni association for a university wants to look at the relationship between the number of years since graduation and the amount of monetary contribution an alumnus makes to the university. He collects data on 50 alumni who have made contributions this year...
September 22, 2012

chemistry
Vacuum filtration is avoided when crystals are isolated from a very volatile solvent. why?
September 21, 2012

chemistry
The suction of a vacuum filtration apparatus is broken before the vacuum is turned off.give reason.
September 21, 2012

chemistry
An Erlenmeyer flask containing a hot solution is not tightly stoppered to prevent solvent loss during cooling. give reasons.
September 21, 2012

chemistry
A hot recrystallization solution is not filtered unless absolutely necessary.give reason.
September 21, 2012

Physics
A ball is thrown from a point 1.38 m above the ground. The initial velocity is 19.9 m/s at an angle of 33.8° above the horizontal. Find the maximum height of the ball above the ground. Calculate the speed of the ball at the highest point in the trajectory.
September 20, 2012

Chemistry
A chemist conducted a recrystallization on 18.5 g of a solid and collected 12.5 g from the first, and 2.7 g from the second recrystallization. Show your calculation and answer the following questions: What is the percent recovery in the first recrystallization? (1.5 marks) ...
September 20, 2012

Chemistry
• A student crystallized a compound from benzene and observed only a few crystals when the solution cooled to room temperature. To increase the yield of crystals, the students chilled the mixture in an ice-water bath. The chilling greatly increased the quantity of solid ...
September 20, 2012

Chemistry
Carborundum (silicon carbide) boiling chips are better than calcium carbonate chips in the recrystallization of an unknown,why ?
September 20, 2012

Chemistry
Carborundum (silicon carbide) boiling chips are better than calcium carbonate chips in the recrystallization of an unknown,why ?
September 20, 2012

Chemistry
The solubility of acetanilide in hot water (5.5 g/100 mL at 100C) is not very great, and its solubility in cold water (0.53 g/100 mL at 0C) is significant. What would be the maximum theoretical percent recovery from the first recrystallization of 0.5 g of acetanilide from 100 ...
September 20, 2012

Chemistry
Why can a water-ethanol solution be used for recrystallization but not a water-hexane solution?
September 20, 2012

Chemistry
The solubility of compound A in ethanol is 0.4 g per 100 mL at 0C and 5.0 g per 100 mL at 78C. What is the minimum amount of solvent needed to recrystallize an 8.0 g sample of compound A? How much would be lost in the recrystallization? Show your work.
September 20, 2012

Chemistry
After treating a coloured solution of a compound with activated charcoal, filtering and drying the product, the colour of the product was grey. What caused the grey colour? How can the grey colour be removed?
September 20, 2012

chemistry
explain the term carbonate error ..
September 17, 2012

Physics
A person walks the path shown below. The total trip consists of four straight-line paths. Path 1 is 40.0 m due east. Path 2 is 170.0 m due south. Path 3 is 120.0 m 30.0° south of west. Path 4 is 190.0 m 60.0° north of west. At the end of the walk, what is the person&#...
September 17, 2012

math
It is estimated that one third of one per cent of the Earth’s surface receives more energy from the sun than the total projected needs for the year 2014. Assuming the Earth’s surface to be 1.97 x 108 square miles. Find the area in acres.
September 16, 2012

Math
a/(a+2)-1 = -(3a+2)/(a^2+4a+4)
September 16, 2012

math
It is estimated that one third of one per cent of the Earth’s surface receives more energy from the sun than the total projected needs for the year 2014. Assuming the Earth’s surface to be 1.97 x 108 square miles. Find the area in acres.
September 13, 2012

math
How many liters of gasoline are there in 165 gal (US) of a methanol-gasoline blend that is 11.0% by volume?
September 13, 2012

math
A chemical distillation tower, 110 m high is supported by cables of length L that reach from the top of the column to the ground at a distance D from the base of the tower. If D is 1/3 the length of a cable, find L and D.
September 13, 2012

Identify 5 characteristics common to plants and describe them?
September 13, 2012

math
Write a number which rounds to 66,000 when rounded to the nearest ten thousand
September 12, 2012

psychology
when kevin started his car in the parking lot, he also turned on the radio to his favorite station,as he entered the street onto the campus, he turned the radio up due to the increased background noise in the car. entering the highway, he again increased the volume until he ...
September 12, 2012

math
Alex spent 3/7 of his money. He gave 1/4 of the remainder to his sister. He had \$120 left. How much money did he have in the beginning?
September 11, 2012

physics
A roller coaster travels 196ft at an angle of 61.1° above horizantally. How far does it travel horizantally?
September 10, 2012

Math
an air traffic controller spots two planes at the same altitude flying towards one another. their flight paths form a right angle at point p. One plane is 150 miles from point p and is moving 450mph. the other plane is moving at 450mph but is 200 miles from point p. write the ...
September 9, 2012

Precalculus
an air traffic controller spots two planes at the same altitude flying towards one another. their flight paths form a right angle at point p. One plane is 150 miles from point p and is moving 450mph. the other plane is moving at 450mph but is 200 miles from point p. write the ...
September 9, 2012

Math
what does -1 E-4 mean when you write it out?
September 6, 2012

Physics
You are traveling on an airplane. The velocity of the plane with respect to the air is 110.0 m/s due east. The velocity of the air with respect to the ground is 39.0 m/s at an angle of 30° west of due north. 1) What is the speed of the plane with respect to the ground? 2) ...
September 5, 2012

algebra
(3,0),0,-4).solve for length, standard form.thank you
September 2, 2012

algebra
(3,0),0,-4).solve for length, standard form.
September 2, 2012

algebra
(3,0),0,-4).solve for the following :
September 2, 2012

Health
August 29, 2012

Math
Find the half-life (in hours) of a radioactive substance that is reduced by 10 percent in 5 hours.
August 28, 2012

physics
A red ball is thrown down with an initial speed of 1.0 m/s from a height of 27.0 meters above the ground. Then, 0.6 seconds after the red ball is thrown, a blue ball is thrown upward with an initial speed of 24.5 m/s, from a height of 0.7 meters above the ground. The force of ...
August 27, 2012

Physics
A tortoise and hare start from rest and have a race. As the race begins, both accelerate forward. The hare accelerates uniformly at a rate of 0.8 m/s2 for 4.4 seconds. It then continues at a constant speed for 13.5 seconds, before getting tired and slowing down with constant ...
August 27, 2012

physics with 6 questions
Two cars start from rest at a red stop light. When the light turns green, both cars accelerate forward. The blue car accelerates uniformly at a rate of 3.3 m/s2 for 3.9 seconds. It then continues at a constant speed for 13.7 seconds, before applying the brakes such that the ...
August 27, 2012

Physic
Type A nerve fibers in humans can conduct nerve impulses at speeds up to 139.8 m/s. How fast is this in mph? This is a question from my physic homework. I have tried converting 139.8 m/s to mile then to hrs and i got .000241 mph. When I input it it said this is not correct. ...
August 26, 2012

physics
A rolling ball moves from x1 = 3.2 cm to x2 = -4.2 cm during the time from t1 = 3.8 s to t2 = 6.1 s. What is its average velocity?
August 23, 2012

math
Estimate. 247 * 974 a. Write your estimate as a number sentence: ________________ b. How I estimated : ________________________________
August 21, 2012

Stats
Question 3 Investment analysts generally believe the interest rate on bonds is inversely related to the prime interest rate for loans; that is, bonds perform well when lending rates are down and perform poorly when interest rates are up. Can the bond rate be predicted by the ...
August 20, 2012

Stats
This assignment requires you to use Excel. In question 1, you will use the charting features. In questions 2 and 3, use the regression tool from the analysis toolpack. There is no template for this assignment. Make sure you explain your answers and provide the regression ...
August 20, 2012

Math
Joelle earns her regular pay of 7.50 per hour for up to 40 hours a week. for each hour over 40 hours of work in a week, joelle is paid 1.5 times her regular pay. how much does joelle earn for a week in which she works 42 hours?
August 14, 2012

psychology
After watching golf on TV several times with her father, 7-year-old Michelle learned how to swing a club even before she actually had one in her hands. What kind of learning took place?
August 12, 2012

health