# David

Most popular questions and responses by David-
## Physics

A 69.5kg football player is gliding across very smooth ice at 2.15m/s . He throws a 0.470kg football straight forward. A) What is the player's speed afterward if the ball is thrown at 16.0m/s relative to the ground? B) What is the player's speed afterward

*asked on May 27, 2014* -
## physics

Suppose 3 mols of neon (an ideal monatomic gas) at STP are compressed slowly and isothermally to 0.19 the original volume. The gas is then allowed to expand quickly and adiabatically back to its original volume. Find the highest temperature attained by the

*asked on January 26, 2011* -
## Chemistry

At equilibrium, the concentrations in this system were found to be [N2] = [O2] = 0.100 M and [NO] = 0.500 M. N2(g) + O2(g) 2NO(g) If more NO is added, bringing its concentration to 0.800 M, what will the final concentration of NO be after equilibrium is

*asked on March 5, 2012* -
## Chemistry

IN my experiment, I was doing a qualitative analysis of Group I and II anions using a flowchart. IN the chart I added 5 drops of 0.1M AgNO3 and several drops of 3M HNO3 to 5 drops of solution and found that a precipitate was formed. Thus it was classified

*asked on April 12, 2009* -
## physics

A copper atom has 29 electrons revolving around the nucleus. A copper ball has 4x10^23 atoms. What fraction of the electrons be removed to give the ball a charge of +9.6uC?

*asked on March 31, 2015* -
## Chemistry

at 25C and 795 torr, carbon dioxide has a solubility of 0.0356 M in water. What is the solubility at 25 C and 2070 torr? ____ M I know that at a given temperature, the solubility of a gas in a liquid is directly proportional to its pressure but how would

*asked on February 16, 2012* -
## finding c: calc

let f(x)=square root x. if the rate of change of at x=c is twice its rate of change at x=1, then c=? what???? i don't get get it. to begin with, i took the derivative if that helps which is 1/(2*sqrtx) . f'(x) = 1/(2*sqrtx) is correct f'(x=1) = 1/2 The

*asked on December 5, 2006* -
## calc help showed work

If the function f has a continuous derivative on [0,c], the the integral(o to c) of f'(x)dx= a)f(c)-f(0) b)absolute value (f(c)- f(0)) c) f(c) d)f'(x)=c e)f"(c)-f"(0) My work: so the the answer to the integral is f(x) and when find the answer from o t0 c,

*asked on December 7, 2006* -
## Math

Eduardo has a red 6-sided number cube and a blue 6-sided number cube. The faces of the cubes are numbered 1 through 6. Eduardo rolls both cubes at the same time. The random variable X is the number on the red cube minus the number on the blue cube. What is

*asked on August 23, 2016* -
## chemistry

When the glucose solution described in part A is connected to an unknown solution via a semipermeable membrane, the unknown solution level rises. Based on this information, what can be said about these two solutions? a.) The unknown solution had the lower

*asked on February 24, 2010* -
## physics

The length of a simple pendulum is 0.79m and the mass of the particle at the end of the cable is 0.24 kg. The pendulum is pulled away from its equilibrium position by an angle of 8.5 degrees and released from rest. Assume that friction can be neglected and

*asked on December 12, 2010* -
## Chemistry

What is going on in the hexane layer at the end of the Group I anion experiment? (when color of hexane layer is yellow you have Br- and when it is brown or purple you have I-.) please explain

*asked on April 12, 2009* -
## Math

in a survey of 290 newspaper readers, 181 of them read the Daily Times, 142 Read the Guardian 117 read punch and each reads at least one of the three papers if 75 read the Daily Times, and the Guardian, 60 read the Daily Times and punch, and 54 read the

*asked on November 11, 2018* -
## AP Chemistry

Determine the volumes of 0.10 M CH3COOH and 0.10 M CH3COONa required to prepare 10.0 mL of buffer of each of the following pH values? a. Ph 3.7 b. pH 5.7 C. pH 5.7 I just need to see how to do one of them and I'll understand how to do the rest.

*asked on April 22, 2015* -
## chemistry

at 20 C the vapor pressure of dry ice is 56.5 atm. if 32 g of dry ice is placed in an evacuated .25 l chamber at a constant temperature of 20 C will all the dry ice sublime

*asked on January 13, 2013* -
## Chemistry

Given that the vapor pressure of water is 17.54 torr at 20 C, calculate the vapor-pressure lowering of aqueous solutions that are 2.40 m in (a) sucrose, C12H22O11, and (b) aluminum chloride. Assume 100% dissociation for electrolytes. Sucrose Delta P = __

*asked on February 19, 2012* -
## Physics

Two identical cars are traveling at the same speed. One is heading due east and the other due north, as the drawing show. What is true regarding the kinetic energies and momenta of the cars?

*asked on October 24, 2010* -
## Chemistry

8-hydroxyquinoline (Q) can complex and precipitate many metals. A mixture of the aluminium and magnesium complexes weighed 1.0843g (MW=459.43; 312.61). When ignited, the mixture decomposed and left a residue of Al203 (MW 101.96) and MgO (MW 40.304)

*asked on August 24, 2014* -
## 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

*asked on September 30, 2012* -
## 6th Grade Math

Estimate a range for each sum. 3.89 + 42.71 + 12.32 I don't understand what to do for "estimating a range".

*asked on January 11, 2010* -
## Physics

A road heading due east passes over a small hill. You drive a car of mass m at constant speed v over the top of the hill, where the shape of the roadway is well approximated as an arc of a circle with radius R. Sensors have been placed on the road surface

*asked on October 1, 2015* -
## Chem

Write a chemical formula. . . Ca2+ and S2-

*asked on July 30, 2016* -
## Chemistry

Suppose you wanted to heat a mug of water (250 mL) from room temperature 25 C to 100 C to make a cup of tea. How much energy (in units of calories and joules) would you need from your microwave?

*asked on January 22, 2012* -
## Math

A rock is thrown upward from a bridge that is 88 feet above a road. The rock reaches its maximum height above the road 0.67 seconds after it is thrown and contacts the road 3.18 seconds after it was thrown. Define a quadratic function, f, that gives the

*asked on October 23, 2015* -
## Math

You are designing a rectangular playground. On your scale drawing, the vertices of the rectangle are (10, –9), (10, –3), and (13, –9). What are the coodinates of the fourth vertex?

*asked on April 13, 2011* -
## Chemistry

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

*asked on September 20, 2012* -
## Math

Simplify the expression 6P3. I don't know how to solve it so if you could help me with it as well i would really appreciate it.

*asked on April 23, 2015* -
## science;chem

The hydrolysis of ethyl acetate (CH3COOC2H5) by sodium hydroxide yields ethanol (C2H5OH) and sodium acetate (NaO2CCH3) by the reaction shown, which follows second order kinetics. In an experiment 500 mL of 0.1 M ethylacetate in water is mixed with 500 mL

*asked on December 16, 2017* -
## Physics

In a repair shop a truck engine that has mass 429 kg is held in place by four light cables (Figure 1) . Cable A is horizontal, cables B and D are vertical, and cable C makes an angle of 37.1∘ with a vertical wall. Tension in cable A is 729 N . a.What is

*asked on October 2, 2015* -
## 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

*asked on September 20, 2012* -
## physics

1.) A vertical spring with a spring constant of 450 N/m is mounted on the floor. From directly above the spring, which is unstrained, a 0.30 kg block is dropped from rest. It collides with and sticks to the spring, which is compressed 2.5 cm in bringing

*asked on December 13, 2010* -
## Chemistry

Why do magnesium, phosphorus, and zinc exhibit slightly higher first ionization energies than the general trend within each of their periods?

*asked on November 10, 2010* -
## sum geometric series

what is the sum of geometric infinite series 3/2+ 9/16+ 27/128+ 81/1024=.... i know the formula is S=a/(1-r) my teacher, he usually transforms into a formula of the sum series and finds out a and r.but i don't how to do that. the pattern i saw is 3/2 +

*asked on April 9, 2007* -
## Science, NATS

Consider the following chemical reaction. Molecular hydrogen and carbon dioxide react to form water and methane. H2+CO2-->H2O+CH4 A)Explain why this equation is not balanced and what law of nature does it break in its current form? B) Astronauts from the

*asked on October 1, 2016* -
## 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

*asked on September 17, 2012* -
## Physics 1

A textbook of mass 1.95 kg rests on a frictionless, horizontal surface. A cord attached to the book passes over a pulley whose diameter is 0.100 m , to a hanging book with mass 3.08 kg . The system is released from rest, and the books are observed to move

*asked on April 6, 2016* -
## Chemistry

Calculate the mass of the precipitate formed when 2.27 L of 0.0820 M Ba(OH)2 are mixed with 3.06 L of 0.0664 M Na2SO4.

*asked on August 13, 2016* -
## 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

*asked on August 27, 2012* -
## chemistry

Fish-liver oil is a good source of Vitamin A. When 0.1232 g of fish liver oil is dissolved in 500. mL of solvent, an absorbance of 0.724 is recorded. When 0.00167 g of Vitamin A is dissolved in 250. mL of solvent, an absorbance of 1.018 is recorded.

*asked on February 8, 2011* -
## History

Use the following statement by Robert Owen to answer the question below: "...but I know that society may be formed so as to exist without crime, without poverty, with health greatly improved, with little if any misery, and with intelligence and happiness

*asked on April 16, 2016* -
## Physics

A man holds a child on his shoulder while watching a football match.how much work is done if the game lasts for 2hours

*asked on January 18, 2018* -
## physics

A board that is 20 cm wide, 5 cm thick, and 3 m long has a density of 350 kg/m^3. The board is floating partially submerged in water do density 100 kg/m^3. What fraction of the volume of the board is floating above water?;

*asked on July 13, 2013* -
## 8th grade math

Hoshi walks 10 meters in 3 seconds. A. What is her walking rate? B. At this rate, how long does it take her to walk 100meters? C. Suppose she walks this same rate for 50sec. How far does she walk? D. Write an equation that represents the distance d that

*asked on August 25, 2011* -
## Elasticity (Physics)

A tunnel of length L=150m, height H=7.2m, and width w=5.8m (with a flat roof) is to be constructed at a distance d=60m beneath the ground. The tunnel roof is be entirely supported by square steel columns, each with a cross sectional area of 960 cm^2. The

*asked on September 9, 2009* -
## Math

theoretically if you roll a number cube 36 times, how many times would you expect to roll the number one? could you also give me explanation? Thank you. and also answer as fast as possible.

*asked on March 13, 2017* -
## Science

Ice at 0 degree celcuis is added to 200g of water initially at 70 degree celcuis in a vacuum flask.When 50g of ice has been added and has all melted the temperature of the flask and contents is 40 degree celcuis.When a further 80g of ice has been added and

*asked on January 8, 2016* -
## help riemann sums

the expression 1/50 (1/50 +2/50+ 3/50+ .....50/50)is a Reimann sum approximation for (everything in the parantheses is square root except the 1/50 outside the paratheses) the answer has to me the integral form so from looking at the formula in my book i

*asked on December 2, 2006* -
## 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

*asked on December 4, 2012* -
## chemistry

Sort these elements into isoelectronic groups. Into three different boxes/sections. Elements: F- O2- Al3+ S2- Ti4+ K+ He Li+ B3+

*asked on September 30, 2013* -
## Biology

Compare and contrast indirect versus direct values of biodiversity, and provide examples.

*asked on October 17, 2014* -
## 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

*asked on September 22, 2012* -
## chemistry

What would be the advantages and disadvantages of using tribasic sodium phosphate (aka trisodium phosphate) to soften water by removing calcium ions?

*asked on April 12, 2009* -
## chemistry

In the reaction N2 + 3H2 -> 2NH3, how many grams of NH3 gas would be formed when H2 gas, having a volume of 11.2 liters at STP, reacts with excess N2 gas? Completly confused, thank you very much for your help :)

*asked on April 6, 2011* -
## Physics

A 283 g air track glider moving at 0.69 m/s on a 2.4 m long air track collides elastically with a 467 g glider at rest in the middle of the horizontal track. The end of the track over which the struck glider moves is not frictionless, and the glider moves

*asked on December 12, 2014* -
## Geometry

According to the given information, segment AB is parallel to segment DC and segment BC is parallel to segment AD.. Construct diagonal A C with a straightedge. It is congruent to itself by the Reflexive Property of Equality. ________________. Angles BCA

*asked on February 25, 2014* -
## Statistics

. Two thousand randomly selected adults were asked whether or not they have ever shopped on the internet. The following table gives a two-way classification of the responses obtained. Have shopped Have never shopped Male 500 700 Female 300 500 Suppose one

*asked on June 11, 2013* -
## CHEMISTRY

A solution of a metal carbonate M2CO3, was prepared by dissolving 7.46 g of the anhydrous solid in water to give 1000cm^3 of solution. 25.0cm^3 of this solution reacted with 27.0cm^3 of 0.100 mol/dm^3 hydrochloric acid. Calculate the relative formula mass

*asked on July 9, 2016* -
## Physics

A scaffold of mass 60 kg and length 5.0 m is supported in a horizontal position by a vertical cable at each end.A painter of mass 80 kg stands at a point 1.5 m from one end. (a)Find the tension in the cable nearer to the painter. (b)Calculate the tension

*asked on May 17, 2010* -
## Physics

A 283 g air track glider moving at 0.69 m/s on a 2.4 m long air track collides elastically with a 467 g glider at rest in the middle of the horizontal track. The end of the track over which the struck glider moves is not frictionless, and the glider moves

*asked on December 14, 2014* -
## chemistry

The suction of a vacuum filtration apparatus is broken before the vacuum is turned off.give reason.

*asked on September 21, 2012* -
## ENGL

These three questions I am having difficulty in solving. Can you help me here. Question 1 - a) Whenever children in the United States turn on the tv, B) they are more likely to encounter violence on the screen. A is an independent clause. A is a dependent

*asked on March 3, 2011* -
## Maths ( permutation and combination)

a town council plans to plant 12 trees along the centre of a main road.It has 4 hibiscus trees, 6 Jacaranda trees, 2 oleander trees. How many different arrangements of these 12 trees can be made if no hibiscus tree is next to another

*asked on September 25, 2016* -
## Chemistry

CH4 + 2O2 -> CO2 + 2H2O When 70 grams of oxygen react with methane, how many liters of CO2 gas are produced?

*asked on January 14, 2012* -
## Chemistry

Barium sulfate, BaSO4 is made by the following reaction. Ba(NO3)2(aq) + Na2SO4(aq)----> BaSO4(s) + 2NaNO3(aq) An experiment was begun with 91.77 g of Ba(NO3)2 and an excess of Na2SO4. After collecting and drying the product, 62.3 g of BaSO4 was obtained.

*asked on April 3, 2010* -
## CHEM - ASAPPP

write the equation for the reaction of fecl2 with k3[fe(cn)6]???

*asked on October 2, 2011* -
## Physics

You swing one yo-yo around your head in a horizontal circle. Then you swing another yo-yo with twice the mass of the first one, but you don't change the length of the string or the period. How do the tensions in the strings differ?

*asked on April 21, 2010* -
## 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?

*asked on August 14, 2012* -
## physics

Some enterprising physics students working on a catapult decide to have a water balloon fight in the school hallway. The ceiling is of height 3.2 m, and the balloons are launched at a velocity of 12 m/s. The acceleration of gravity is 9.8 m/s2 . At what

*asked on January 11, 2011* -
## dbs

Determine the rate of interest at which a sum of money will become 216/125 times the original amount in 1 and a half years, if the interest in compounded half

*asked on September 24, 2017* -
## Social studies

Which of the following is no longer allowed in the Atlantic Provinces? A)cod fishing B)fishing C)aquaculture**** D)fish processing Correct?

*asked on May 4, 2017* -
## english

Identify the subjects of the following sentences. Jacob's favorite poker game is Texas Hold'em

*asked on March 8, 2012* -
## Physics

A certain spring stretches 5.3 cm when it supports a mass of 0.65 kg . If the elastic limit is not reached, how far will it stretch when it supports a mass of 10 kg ?Answer in units of cm

*asked on January 11, 2011* -
## english

a letter to your uncle in american asking him to help you pay your school fees for this term.

*asked on May 9, 2016* -
## chemistry

A hot recrystallization solution is not filtered unless absolutely necessary.give reason.

*asked on September 21, 2012* -
## Chemistry

2C6H6(l) + 15O2(g) -> 12CO2(g) + 6H2O(l) + 6542 kJ If the heat from burning 7.000 g of C6H6 is added to 5691 g of water at 21 degrees C what is the final temperature of the water?

*asked on February 10, 2012* -
## intro to chemistry

A sample of nitrogen has a volume of 50.0L at a pressure of 760mmHg. What is the volume of the gas at each of the following pressures if there is no change in temperature? A. 1500mmHg B. 2.0atm C. 0.500atm

*asked on October 11, 2010* -
## calc

the volume of a cylindrical tin can with a top and a bottom is to be 16*pi cubic inces. if a minimum amont of tin is to be used to construct the can, what must be the height, in inches, of the can? volume of cyliner is pi*r^2*h do i like take derivitive of

*asked on December 8, 2006* -
## math

Marta’s math textbook weighs mc017-1.jpg of a pound less than 4 times the weight of the book she is reading for her language arts class. If the weight of the math textbook is mc017-2.jpg pounds, which shows the correct equation and value of x, the weight

*asked on June 10, 2016* -
## Physics

An automobile and a truck start from rest at the same instant, with the automobile initially at some distance behind the truck. The truck has a constant acceleration of 2.15m/s2 , and the automobile an acceleration of 3.47m/s2 . The automobile overtakes

*asked on June 8, 2015* -
## Physics

In a cyclotron (one type of particle accelerator), a deuteron (of mass 2.00 u) reaches a final speed of 8.4% of the speed of light while moving in a circular path of radius 0.551 m. What magnitude of magnetic force is required to maintain the deuteron in a

*asked on October 5, 2010* -
## 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

*asked on August 27, 2012* -
## AP Chemistry

A typical bathtub can hold 94 gallons of water. Calculate the mass of natural gas that would need to be burned to heat the water for a tub of this size from 59 ◦F to 101 ◦F. Assume that the natural gas is pure methane (CH4) and that the products of

*asked on October 26, 2016* -
## Math

A rooming house has three rooms that contains four beds, three beds and two beds respectively. In how many ways can nine quests be assigned to these rooms? The book says it is 1260. I have no idea how they got this. I know it requires combinations. Could

*asked on April 16, 2011* -
## chemistry

Most natural gas consists of about 90% methane, CH4. Assume that the solubility of natural gas at 20 C and 1 atm gas pressure is about the same as that of CH4, 0.02 g/kg water. If a sample of natural gas under a pressure of 20 atm is kept in contact with

*asked on March 8, 2010* -
## Math

A baker is decorating the top of around cake with cherries. The diameter of the cake is 9.5 inches. Each cherry is 0.75 inches in diameter. About how many cherries will the baker need to decorate the perimeter of the top of the cake?

*asked on February 14, 2018* -
## chemistry

Vacuum filtration is avoided when crystals are isolated from a very volatile solvent. why?

*asked on September 21, 2012* -
## Chemistry

The experiment that I did in lab consisted of performing a qualitative analysis of group 1 and 2 cations and anions. The first thing that I did was to add 5 drops of 3M HCl, centrifuge it, and to observe whether a precipitate would form. It did and in the

*asked on April 12, 2009* -
## Physics 1

A 50 kg cannonball hits a war tank vehicle of 12,000 kg that is initially at rest. The cannonball embeds in the tank and both move at the same velocity for 50 cm until they both come to a rest. What is the initial velocity of the cannonball if the

*asked on March 8, 2016* -
## Calculus

Project Setup:You work for a company that manufactures cylindrical steel drums that can be used to transport various petroleum products. Your assignment is to determine the dimensions (radius and height) of a drum that is to have a volume of 1 cubic meter

*asked on April 17, 2019* -
## Social Studies

Which of the following correctly pairs a branch of the U.S. government and its power? 1. A. legislative: interprets laws B. executive: makes laws C. executive: enforces laws---- D. judicial: enforces laws 2. Which of the following is an example of the

*asked on August 26, 2018* -
## Physics

Two cars collide as shown in the figure. The yellow car is initially heading east and has a mass of 1000 kg. The red truck is initially heading north and has a mass of 2000 kg. The two vehicles collide, stick together, and veer off at a velocity of 16 m/s

*asked on November 10, 2015* -
## probability

Consider an arrival process whose interarrival times are independent exponential random variables with mean 2 (and consequently variance equal to 4), and consider the interarrival interval S seen by an observer who arrives at a fixed time t∗, as in the

*asked on November 27, 2018* -
## chem help

a scuba diver breathing normal air descends 100m of depth, where the total pressure is 11 atm. What is the partial pressure of oxygen that the diver experiences at this depth? Can someone help out on this question? Make a ratio: 11atm/1atm= P/partial

*asked on March 19, 2007* -
## Calculus 2

Suppose that a spring has a natural length of 25 cm, and that 8 J of work is needed to stretch from a length of 50 cm to 80 cm. How far beyond its natural length will a force of 32 N keep the spring stretched? **I've tried calculating the spring

*asked on April 25, 2016* -
## physicss

Two point charges experience an attractive force of 5N when they are separated by 1m.what force do they experience when their separation is 2m? What is the value of the charges Using coluomb's law F=KQ1Q2/r^2 5=8.99*10^9*Q1*Q2/1

*asked on January 10, 2016* -
## chemistry

I want to make sure I am correct in classifying whether the following properties of hydrogen are chemical or physical. thanks 1. hydrogen will burN in in oxygen to form water. CHEMICAL 2. hydrogen does not support combustion. CHEMICAL 3.hydrogen is usually

*asked on April 8, 2014* -
## chem

confused about this one. 2 samples of water of equal volume are put into dishes and kept at room temp for several days. the water in the first dish is completely vaporized after 2.8 days while the water in the second dish takes 8.3 days to completely

*asked on March 29, 2007* -
## Math

A bucket begins weighing 15 pounds, including the sand it holds. The bucket is to be lifted to the top of a 50 foot tall building by a rope of negligible weight. However, the bucket has a hole in it, and leaks 0.1 pounds of sand each foot it is lifted.

*asked on April 30, 2016* -
## Maths

A student spent 2 /9 of his pocket money on beverage and 1 /4 on books. What? fraction

*asked on November 14, 2017* -
## Physics

You have a brass ring of inside diameter 10.00 cm that is at 20.0oC. You want to slip this ring over an aluminum rod that is at 20.0oC and has a diameter of 10.01 cm. a. To what temperature do you have to heat the ring to slip it over the rod? b. Once you

*asked on December 4, 2014*