Saturday

April 30, 2016
Total # Posts: 1,202

**writing**

so i have to write a research paper(3-4 pages) on this topic 'does lack of sleep affect heart rate' how do i do that...this is the first time i write a research paper so i need help..thanks
*February 5, 2011*

**physics**

The engines of a 1.20 x 10^5 N rocket exert an upward thrust of 2.00 x 10^5 N for 1.50 minutes upon lift off. What is the impulse exerted on the rocket? What is the velocity of the rocket at the end of the 1.50 minute period? physics - bobpursley, Thursday, February 3, 2011 at...
*February 3, 2011*

**physics**

I don't understand where the 90 comes from
*February 3, 2011*

**physics**

The engines of a 1.20 x 10^5 N rocket exert an upward thrust of 2.00 x 10^5 N for 1.50 minutes upon lift off. What is the impulse exerted on the rocket? What is the velocity of the rocket at the end of the 1.50 minute period?
*February 3, 2011*

**Chemistry**

Hydrogen gas has been suggested as a clean fuel because it produces only water vapor when it burns. If the reaction has a 95.4% yield, What mass of hydrogen forms 94 Kg of water?
*February 3, 2011*

**Chemistry**

Maxine is studying about electrolytes in her chemistry class. The teacher asks her to test 4 different solutions to determine how well each one conducts electricity. which solution will best conduct electric current? a) HC2H3O2 b) C2H5OH c) KOH d) H2O2
*February 3, 2011*

**chemistry**

Calculate the moles of Cl atoms in 0.0565g of C2H4CL2 i got 6.87 x 10^20 mol Cl atoms <-- is that right?
*February 3, 2011*

**Physic**

How does doubling the mass of one object and tripling the distance between another object change the gravitational force betweem them? FG = G M1 M2 / r2 a. Force changes by 2/3 b. Force changes by 2/9 c. Force increases by 9 d. Force decreases by 3 e. No change in force
*February 2, 2011*

**psychology**

the question: Some size/distance cues are useful for distant objects, others for close objects. Provide one example of a cue that would be good for near objects, and one for distant objects. Explain why the cues you have selected would be less useful for objects at other ...
*February 2, 2011*

**Math**

Is the price of a piece of cloth a function of the length of the cloth? Explain
*January 31, 2011*

**Math**

Is the price of a piece of cloth a function of the length of the cloth? Explain
*January 31, 2011*

**physics**

Two point charges, 4.0×10-6 C and -1.0×10-6 C, are located on the x axis at = -1.0 cm and = 3.0 cm. (a) Determine the electric field at the origin. (b)Determine the x coordinate of a point on the positive x axis where the electric field is zero; i.e., a test charge...
*January 30, 2011*

**physics**

Inside a perfect conductor 1)the electric potential is zero throughout, even at the surfaces. 2)the electric field is zero throughout, even at the surfaces. 3)the electric potential is constant throughout, even at the surfaces. 4)none of the above is correct. I have no idea??
*January 25, 2011*

**physics**

Never mind I figured it out:)
*January 23, 2011*

**physics**

A charge Q = -520 C experiences a downward force of 0.04 N. What is the electric field in N/C at the point where the charge is located? Take upward to be positive. I know that E=Kq/r^2 therefore E= (9.0*10^9Nm)(-520*10^-6c)/r^2 I'm not sure how to get the distance and what...
*January 23, 2011*

**Algebra**

find the measure of an angle whose supplement measures two times its measure
*January 22, 2011*

**Math**

is 1/2 2?
*January 5, 2011*

**Math**

1/2x > -3
*January 5, 2011*

**Math**

-3x < 0
*January 5, 2011*

**Math**

What happens to the inequality symbol when you do the following to each side of an inequality? 1. Subtract a negative number
*January 5, 2011*

**Math**

1/2x > -3
*January 5, 2011*

**Math**

18 < -2m would the anser be m < -9?
*January 5, 2011*

**Math**

A truck tire travels about 11 feets in 1 full rotation. What is the diameter of the wheel, to the nearest inch?
*December 16, 2010*

**physics**

A 1300 sports car accelerates from rest to 95KM/H in 7.0S .What is the average power delivered by the engine?
*December 15, 2010*

**chemistry**

what is the total number of joules released when a 5.00 gram sample of water changes from liquid to gas at 100 degrees Celsius?
*December 15, 2010*

**physics**

Assume that the pressure is one atmosphere and determine the heat in joules required to produce 3.23 kg of water vapor at 100.0 °C, starting with (a)3.23 kg of water at 100.0 °C and (b)3.23 kg of liquid water at 0.0 °C
*December 14, 2010*

**physics**

A piece of glass has a temperature of 72.0 °C. Liquid that has a temperature of 37.0 °C is poured over the glass, completely covering it, and the temperature at equilibrium is 50.0 °C. The mass of the glass and the liquid is the same. Ignoring the container that ...
*December 13, 2010*

**Physics**

A cube of solid aluminum has a volume of 1.00 m^3 at 20 degree C. What temperature change is required to produce a 100-cm^3 increase in the volume of the cube? I know you are supposed to use: DeltaV=Beta*Vo*DeltaT. But I don't know what Beta is and the ones I have found ...
*December 12, 2010*

**PHYSICS**

A toy car in the figure below runs off the edge of a table that is h = 1.375 m high. The car lands d = 0.375 m from the base of the table.How fast was the car going on the table?
*December 11, 2010*

**PHYSICS**

You accidentally throw your car keys horizontally at 10.0 m/s from a cliff 78 m high. How far from the base of the cliff should you look for the keys?
*December 11, 2010*

**physics**

an arrow of mass .04 kg is pulled back 10 cm in the bow, having a force of 25.2 N. It is released 1.5m from the ground...how far will the arrow fly? (all of the energy from pulling it back converts into the flying arrow)
*December 6, 2010*

**Physics **

Rubber Band A 156 g hockey puck is attached to a rubber band and rotated with an angular speed of 9.8 rad/s on frictionless horizontal ice. It takes a force of 1.12 N to stretch the rubber band by 1 cm. (a) If the original length L of the rubber band is 1 m, by how much (in m...
*December 3, 2010*

**chemistry**

thanks for the explanation!!!
*December 1, 2010*

**chemistry**

2. A 350 mL buffer solution containing 0.15 M HF and 0.150 M NaF is reacted with sodium hydroxide. What mass of NaOH can this buffer neutralize before the pH rises above 4.0? If the same volume of buffer was 0.35 M in HF and 0.35 M in NaF then what mass of NaOH could be ...
*December 1, 2010*

**chemistry**

For each of the following solutions, calculate the initial pH and the final pH after adding 0.010 mol of HCℓ. a) 500.0 mL of pure water i'm not sure how to do this question.. would the equation be h20+h30 equilibrium arrows h30+h20
*December 1, 2010*

**physics**

A 910 kg sports car slows down to 6.0 m/s to read a cross street sign. The 1440 kg pick-up truck following the sports car fails to see that the sports car has slowed and continues traveling at 17.0 m/s. The pick-up slams into the sports car. With what velocity will the two ...
*November 29, 2010*

**physics**

i read the question wrong..thank for the help
*November 29, 2010*

**physics**

A 45.00 kg child standing on a frozen pond throws a 0.60 kg stone to the east with a speed of 5.80 m/s. Neglecting friction between child and ice, what is the speed (in m/s) of the child after throwing the stone? I'm kind of confused about the masses..
*November 29, 2010*

**CAL 1**

DERIVATIVE f(x)=4t+1 (x,x+2)
*November 28, 2010*

**cal 1 **

Find the area of the indicated region f(x)=(4-x^2) between(0,2)with 4 equal subintervals (left endpoints)
*November 27, 2010*

**math**

find all points on the hyperbola y=1/x, that are closest to the origin on (1/2,2)
*November 27, 2010*

**cal 1**

f(x)= (1-sinx) interval (0≤x≤2π) find where the function is increasing decreasing.. i know that f`(x)=1-sinx it is equal to zero when x=pi/2 im stuck there..
*November 26, 2010*

**chemistry**

oops..i posted this question twice
*November 25, 2010*

**chemistry**

a 5.55g sample of a weak acid with ka=1.3*10^-4 was combined with 5.00ml of 6.00 M NAOH and the resulting solution was diluted to 750mL. The measured pH of the solution was 4.25. what is the molor mass of the weak acid. if used the formula pH=kpa+log(base/acid) Ph=3.89+log(6....
*November 25, 2010*

**chemistry**

a 5.55g sample of a weak acid with ka=1.3*10^-4 was combined with 5.00ml of 6.00 M NAOH and the resulting solution was diluted to 750mL. The measured pH of the solution was 4.25. what is the molor mass of the weak acid. if used the formula pH=kpa+log(base/acid) Ph=3.89+log(6....
*November 25, 2010*

**chemistry**

A 20ml sample of .125M diprotic acid solution was titrated with .1019M KOH.the constants for the acid are k1=5.2*10 ^-5 and K2=3.4*10 ^-10. What added volume of base does each equivalence point occur? i got .0254L for the first one and .0508 for the second. Can anyone check if...
*November 24, 2010*

**physics**

What is the original compression distance of the spring? Thought it would be zero but that isn't right.
*November 23, 2010*

**physics**

a 3.5 kg block is accelerated from rest by a compressed spring of spring constant 640 N/m. The block leaves the spring at the springs relaxation length.The block then travels over a horizontal floor with coefficient of kinetic friction 0.25. The friction force stops the block...
*November 23, 2010*

**physics**

never mind i got the question:)
*November 23, 2010*

**physics**

A 2.606 kg block is on a horizontal surface with ìk = 0.160, and is in contact with a lightweight spring with a spring constant of 577 N/m which is compressed. Upon release, the spring does 7.212E-1 J of work while returning to its equilibrium position. I found the ...
*November 23, 2010*

**physics**

the next part is What is the speed of the block when it hits the spring? i did 1.42=.5mv^2(final)-.5mv^2(initail) The final velocity woulf be zero so 1.42=.5(2.8)v^2 v=1.01 im not sure what i did wrong
*November 23, 2010*

**physics**

A moving 2.8 kg block collides with a horizontal spring whose spring constant is 215 N/m (see figure). The block compresses the spring a maximum distance of 11.5 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.48...
*November 23, 2010*

**physics**

The force F = (3.2, -7.1) N acts on a mass of 1.15 kg. At time t = 0 s, the mass has a velocity v0 = (-0.46, 0.36) m/s. What is the initial kinetic energy (in J)? i know that k=.5mv^2 so the answer i got was (.12167,0.07452) but i'm not sure what to do from there?
*November 22, 2010*

**physics**

The force F = (3.2, -7.1) N acts on a mass of 1.15 kg. At time t = 0 s, the mass has a velocity v0 = (-0.46, 0.36) m/s. What is the angle (in degrees) of the initial velocity, measured counter-clockwise from the +x-axis? I got 38.04 degrees but isn't the right answer
*November 21, 2010*

**physics**

A 2.20 kg box slides down a rough incline plane from a height h of 1.39 m. The box had a speed of 2.77 m/s at the top and a speed of 2.34 m/s at the bottom. Calculate the mechanical energy lost due to friction
*November 21, 2010*

**physics**

A constant force of 48.7 N, directed at 34.1° from horizontal, pulls a mass of 15.1 kg horizontally a distance of 2.77 m. Calculate the work done by the force.
*November 21, 2010*

**math**

A painter leans a ladder against a vertical wall. The top of the ladder is 7 meters above the ground. When the bottom of the ladder is moved 1 meter farther away from the wall, the top of the ladder is 5 meters above the ground. What is the length of the ladder? Round to the ...
*November 17, 2010*

**math**

Three rectangles have exactly the same area. The dimensions of each rectangle (as length and width) are a and b; a – 3 and b + 2; and a + 3 and b – 1. Find the area of the rectangles.
*November 17, 2010*

**math**

Three rectangles have exactly the same area. The dimensions of each rectangle (as length and width) are a and b; a – 3 and b + 2; and a + 3 and b – 1. Find the area of the rectangles.
*November 17, 2010*

**Physics **

A cylinder with a piston is filled with ideal gas. The gas temperature is held at 450 K. The cylinder is heated by an oven through a square metal rod connected between the oven and the cylinder. The rod has sides d = 2 cm and length L = 2.3 m. (a) If the oven is held at 850 K...
*November 16, 2010*

**chemistry**

For all deexcitations that result in the visible spectrum of hydrogen, what is n ?
*November 15, 2010*

**chemistry**

The X-X bond energy in the hypothetical gas, X2 is 153 kJ/mol. a. How much energy, in joules, is required to break the bond in a single X-X molecule? b. What wavelength of electromagnetic radiation would have the energy required to break the X-X bond? c. In what region of the ...
*November 15, 2010*

**chemistry**

The red line in the Helium spectrum is longer than the red line in the hydrogen spectrum. What does that tell us about the distance between n2 and n3 in helium as compared with the distance between n2 and n3 in hydrogen?
*November 15, 2010*

**chemistry**

In the emission spectrum of hydrogen, some lines are in the infra red range. h l Suggest an electron transition (specify n and n) that is in this range and calculate its corresponding wavelength and delta E.
*November 15, 2010*

**algebra**

are you sure? thank you :)
*November 10, 2010*

**bobpursley???**

i did that and i also wrote the answers next to each question and i just want to know if they are right. are they right? please respond
*November 10, 2010*

**science**

what is the difference between a control and a variable
*November 10, 2010*

**science**

thank you :)
*November 10, 2010*

**science**

what is concentration plese say it in an easy to understand answer thank you!
*November 10, 2010*

**8th grade**

According to the U.S. Census Bureau in 2009 there were 21,854,374 veterans in the United States. Veterans of the Korean War accounted for 12.4% of that total, while 10.7% were veterans of World War II. What is the positive difference between the numbers of veterans of the ...
*November 9, 2010*

**math**

According to the U.S. Census Bureau in 2009 there were 21,854,374 veterans in the United States. Veterans of the Korean War accounted for 12.4% of that total, while 10.7% were veterans of World War II. What is the positive difference between the numbers of veterans of the ...
*November 8, 2010*

**11th grade physics**

the horizontal range of a projectile is 4 root 3 times of its maximum height. calculate the angle of projection.
*November 8, 2010*

**11th grade physics**

if action and reaction are always equal and opposite, why dont they always cancel each other and leave no force for acceleration of the body?
*November 8, 2010*

**11th grade physics**

find the value of 60 joule per minute on a system which has 10 cm,100gm, and 1 minute as fundamental units.
*November 8, 2010*

**11th grade chemistry**

thank you so much drbob222. u are a genius. could you check out my physics questions too?
*November 8, 2010*

**11th grade chemistry**

a vessel contains 12 gm of methane gas at t degree celcius temp. and 1 atm. pressure. when the temp. is increased by 10 degree celcius at the same volume, the pressure increases by 10%. calculate the volume and initial temp.
*November 8, 2010*

**math**

when is these rational function equal to zero? 6x^2/(x^3+1)^2=0 -2x/(x^2-1)^2=0
*November 7, 2010*

**math**

verify that the function satisfies the hypothesis of the mean value theorem on the given interval. then find all numbers c that satisfy the conclusion of the mean value theorem. f(x) = x/(x+2) , [1,4]
*November 7, 2010*

**calculus**

use the methods of this section to sketch the curve. y=x^3-3a^2x+2a^3, where a is a positive constant. What do the members of this family of curves have in common? How do they differ from each other?
*November 7, 2010*

**Statistics**

Are these statements true or false? 1. The sample mean, the sample proportion and the sample standard deviation are all unbiased estimators of the corresponding population parameters. 2. If the population is normally distributed with known variance then the sample mean may not...
*November 5, 2010*

**math**

what is the best parking space/shortest that would take the from store 1 to store 2 and back to the car?use the following information: -the distance between store 1 to store 2 is 25 yds wide. -driveway between the sidewalk and parking lot is 10 yds this all they give me please...
*November 4, 2010*

**Math**

y = |x − 4| + 8 Find the x-coordinate of the vertex of the graph. And the y-coordinate of the vertex of the graph. Please help me, I'm stuck!
*November 3, 2010*

**HIstory**

Why did congress feel that construction was a confessional task and not a presidential task?
*November 3, 2010*

**spanish**

what am i doing wrong??
*November 1, 2010*

**spanish**

¿Quién va a preparar la ensalada? Mirta y Lidia Your response: mirta y lidia las va a preparar 3.¿Quién va a cocinar la paella? Alberto y su novia Your response: alberto y su novia los va a cocinar. ¿Quién va a limpiar el apartamento ...
*November 1, 2010*

**Halloween**

It's saturday and halloweens tomorrow. But I was wondering is trick or treating sopost be today or tomorrow? I've heard peolple going today and many people say tomorrow. I know sunday is an school night and some people wiill be at church. I have no idea if I should ...
*October 30, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x= y=
*October 29, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x=? y=? i ...
*October 29, 2010*

**CALC HARD...**

i did get that and i got farther than that but then got completely lost
*October 29, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x=? y=? i ...
*October 29, 2010*

**chemistry**

consider the following reactions O+N2->NO+N Ea=315kj/mol Cl+H2->HCl+H Ea=23kj/mol Why is the activation energy for one much lower that the other. The frequency factor is very close in value for the two. Assume they are the same compute the ratio of the reaction constants...
*October 29, 2010*

**cant post a question **

i tried posting a question but it says that i cant have links in my question but i didnt have any? Anyone know hat to do?
*October 28, 2010*

**chem/math**

thanks that helps alot
*October 28, 2010*

**chem/math**

I need to fid the activation energy but i forgot how to solve for Ea 4.58*10^-15=e^(Ea/2537.02) can you show the work thank you
*October 28, 2010*

**Management**

what economic, social , and political forces have made employee traininng even mor eimportant today than in the past?
*October 28, 2010*

**calculus**

find the absolute maximum and minimum values of f on the given interval f(x)= (x^2-4)/(x^2+4), [-4, 4]
*October 28, 2010*

**chemistry**

help
*October 28, 2010*

**physics**

Mary and John are on opposite sides of a seesaw. Mary has 3x the mass of John. If Mary is sitting at a distance of .5m from the fulcrum, how far must John site in order to keep it balanced.
*October 27, 2010*

**calculus**

Use a linear approximation (or differentials) to estimate the given number (2.001)^5
*October 27, 2010*

**physics**

A 70kg man stands on a bathroom scale in an elevator. As the elevator starts moving, the scale reads 90kg Is the elevator acceleration up or down, is the elevator moving up or down?
*October 27, 2010*