# Posts by bobpursley

Total # Posts: 44,134

**Chemistry**

B is correct.

*March 22, 2017*

**Math**

Well, if blue probility is .2, then red has to be less, so if pr<.2, that is a valid probility for red.

*March 22, 2017*

**Physics**

Adapt this problem to your problem: I do not understand your picture, but this should guide you. https://www.physics.wisc.edu/undergrads/courses/spring09/248/HWSolutions/HW12Solutions.pdf

*March 22, 2017*

**Ethics**

It is the question. Consider the biblical story of the Good Samaritan. How many passed by the injured and beaten man before the good samaritan provided for his care? Consider what Doctors without Borders tries to do, and the impediments put in their way. Consider Medicaid and ...

*March 22, 2017*

**Algebra**

Isn't it proved by definition? The angle whose sine is the sine of theta, is theta.

*March 22, 2017*

**physics**

the average velocity is 1rev/second, it want for 30 seconds, displacement=avgveloicty*time=30rev

*March 22, 2017*

**calculus review please help!**

Mean Value Theorem for Integrals. A variation of the mean value theorem which guarantees that a continuous function has at least one point where the function equals the average value of the function. Mean value= (f(1)+f(-1))/2 = (-8+8)/2=0 if f(x)=0=x^3-9x, the the one point ...

*March 22, 2017*

**Physics**

http://www.jiskha.com/display.cgi?id=1490218992

*March 22, 2017*

**chem**

constant pressure... V1/V2=T1/T2 .67/1.12=(61+273)/(273+Tc) solve for Tc , the celcius temp for the new volume.

*March 21, 2017*

**Chemistry**

moles Al=.5/27=.0185 Moles CuCl2=3.5/134.5= 0.0260 the balanced equation requires 3/2 moles CopperIIChloride/Al you have .0260/.0185=1.20 so you dont have a 1.5 ratio, you have too little CuCl2, and it is the limiting reactant

*March 21, 2017*

**Science**

constellations in the North Sky and South sky may not always be visible because of Earth tile and latitude from which observed.

*March 21, 2017*

**Physics**

vfinal=vinitial+at you have given vinitial, acceleration. You want the time t. So what final velocity are you aiming for, vfinal?

*March 21, 2017*

**MATH**

6.5m*100cm/1m=your answer is wrong.

*March 21, 2017*

**Maths**

3. 63-17+19=?

*March 21, 2017*

**English**

That is a rather lengthy topic...I suggest you narrow it.

*March 21, 2017*

**child development**

and the following guidances are...??? If one can, ignore largely the negative behaviours and reinforce the positive behaviours.

*March 21, 2017*

**Chemistry**

Mr????? Do you mean the molecular mass? I assume so. it is 44amu, or 44 grams/mole CaCO3 >>>> CaO + CO2 moles CaCO3= 1000g/(100g/mol=10moles so according to the balanced equation, you should get 10 moles CO2, or 440 grams.

*March 21, 2017*

**Calculus**

<<Cross sections of the solid perpendicular to the y-axis are semicircles>> Somehow, I am not visulizing this. so the base of the solid is in the xy plane, so its altitude must be in the k direction. For the k direction to be semicircles, the shape of the solid has...

*March 21, 2017*

**Calculus**

What is this x-5+5?

*March 21, 2017*

**english Grammar**

Matt likes fish

*March 21, 2017*

**Maths, dynamics**

x=INT v(t)dt =5/6*t^6 i + 4/6 t^6 j + 1/4*t^4k+C given t=0 x=i+2J i+2j=i(5/6(0)+2/3 (0)j+Ok+C C=i+2j

*March 21, 2017*

**Maths, dynamics**

F=Ma a=F/m=225/45 t^4-90/45 t^2-225/45 a=5t^4-2t^2-5 v=int a(t)dt =t^5-2/3 t^3-5t+C given at t=O, v=2 C=2 if v=t^5-2/3 t^3-5t+2 then x=INT v(t)dt x=1/6 t^6+1/6 t^4 +2.5t^2+2t+C given x(o)=6 implies then C=5

*March 21, 2017*

**Trigonometry**

if sinx=-1/2, then cosx=sqrt(1-1/4)=sqrt(3/4)=sqrt3 /2 sin(2x)=2*(-1/2)(sqrt3 /2) = -1/2 sqrt3

*March 20, 2017*

**Trigonometry**

1/ctn=tan=sin/cos=sin/(1-sin^2)

*March 20, 2017*

**SCIENCE**

correct, however, these days news comes on and I have a strong desire to bounce my TV off the wall, number 3 :) .

*March 20, 2017*

**Chemistry**

Increase.

*March 20, 2017*

**Art**

1.)Inventors often work to find faster, more efficient ways of completing a task. How did Samuel F.B. Morse use his artistic ingenuity to create a more efficient telegraph machine? He used only one wire....

*March 19, 2017*

**chemistry**

moles NaOH=.015*.1=.0015moles Moles HCl=.025*.1=.0025 moles excess acid= .0010 moles concentration=.0010/.040 moles/liter pH=-log(H+)=-log(.025)=1.60 pretty acidic

*March 19, 2017*

**chemistry**

NH3? PV=nRT n=PV/RT mass/molmassNH3= PV/RT solve for mass. change temps to Kelvins, and use R in the units of mmHg*Liters/Kelvin

*March 19, 2017*

**physics**

if the "apart" is from center to center distance, .25=kqq/.4^2 solve for q Coulomb's law

*March 19, 2017*

**science**

greater at the higher elevation.

*March 19, 2017*

**physics**

momentum is conserved. 3*5+8*(-3)=(3+8)V V=(15-24)/11=-9/11

*March 19, 2017*

**Chemistry**

you are dreaming thinking you can dump homework here.

*March 19, 2017*

**chemistry**

Heat=mass*specHeat*changeinTemp Notice you are given specific heat in J/gK. the same value applies with units kJ/kg-K

*March 19, 2017*

**math**

multiple of three:3 or 6 pr (3or6)=2/6=1/3 pr(not 3or6)=1-1/3=2/3

*March 19, 2017*

**ELECTRICITY AND MAGNETISM**

Vt=k(q1/3+ q2/4)

*March 19, 2017*

**ELECTRICITY AND MAGNETISM**

let the distance from P to each charge be d1,d2 energy=kq3(1/d1+1/d2)

*March 19, 2017*

**College**

what is sqrt ( 450^2+725^2)

*March 18, 2017*

**Algebra**

126=M(.03)+(4000-M)*.04) where M is at 3 percent. 126=m(.03-.04)+160 M= 34/.01= 3400 and 4000-M=600

*March 17, 2017*

**calculus**

it is of the form inf/inf. taking the derivatives. it is not clear to me is the +1 in the exponent or not, I assume not. lim= (5)/(5))*(4x)(5) lim= 1^inf * 5=5

*March 17, 2017*

**calculus**

you do have a 0/0 form Using Hospital's rule then lim= (e^x+e^-x-2)/(x+cosx) Lim= 0/1=0

*March 17, 2017*

**physics**

let tension right and left=Tr,Tl Tr+Tl=69*g now sum of moments about the right end.. 69g*2.8+Tl*12.5=0 solve for Tl in that equation, then go back to the first equaion, and solve for Tr

*March 17, 2017*

**Chemistry**

Bi2S3 (s) <-> 2Bi3+ (aq) + 3S2- (aq)

*March 17, 2017*

**PHYSICS**

KE at impact=PE at start= m*g*h

*March 17, 2017*

**Physics**

is this positive charge current, or electron current? It matters. Us your hand rules in your text.

*March 17, 2017*

**Physics**

the type of charge, its direction,and direction of the magnetic field. Does your text show you right hand,left hand rules? Surely it does.

*March 17, 2017*

**Physics**

surely your text answers these questions....

*March 17, 2017*

**Physics**

oops, you should have caught my error. You reduced distance by 1/2, so B is twice or .2T

*March 17, 2017*

**Physics**

B=k I/r so if you reduce r by a factor of 1/10, B is now x10, or 1 Tesla

*March 17, 2017*

**chemistry**

balance the chemical reaction Mg + 2HCl>>>H2 + MgCl2 so you need the same number of moles of Mg as you get in H2. molesH2=100/2=50 moles molesMg=same gramsMg=atomicmassMg*50=24.3*50 grams.

*March 17, 2017*

**Algebra**

John has to be 16. Something is wrong with the sentence, punctuation?

*March 17, 2017*

**science**

You typing makes we wonder i i i force is inversley prop 10E-5/F=( 3^2/20^2) F=400/9 E-5 N at 3 cm one 100 cm,that is 5 times as far.. F=1E-5 /25=4E-7 at 100cm

*March 17, 2017*

**Physics**

resistance=Ro(1+.0047T) Ro=10 ohm, given check: R@100=10(1+.0047*100)=10(1+.45)=15ohm 30=10(1+.0047T) 3=1+.0047T T=2/.0047=426C

*March 17, 2017*

**Math**

if those are absolute value signs, then all have to be positive,answer B. However, it is a confusing question.

*March 16, 2017*

**Math7/8**

with replacement Pr(R,R)=3/8*3/8 without replacement Pr(R,R)=3/8*2/7

*March 16, 2017*

**algebra**

.45V1+.90(120-V1)=.6*120 solve for V1, then 120-V1

*March 16, 2017*

**chemistry**

I assume your m should be Molarity, M. mass=molartiy*molmass*volumeinLiters mass=.1*molmassBenzoicAcid*.1m^3 so the mom mass is 122g/mole, so we have mass=.1 Mole/liter*122g/mole*.1 Liter= 1.22 grams check my thinking.

*March 16, 2017*

**Language art 4th grade**

got or gave. Answer D.

*March 16, 2017*

**Algebra**

Do you do matrix algebra on your calculator? coats, shirts, dresses, cost in augmented matrix form: 5,5,6,77 1,8,6,67 3,3,2,43 Now if you want to do it manually as a 3x3 set 5x+5y+6d=77 and so on, then solve it with pencil and paper. The augmented matrix is much faster..

*March 16, 2017*

**Physics**

displacement: 860*.75-720*1.5 East distance : add the above avgvelocity=displacement/total time avg speed: distance/total time

*March 16, 2017*

**health class**

true.

*March 16, 2017*

**physics**

effort=1/.8 * 50*9.8*k what is k? that is the mechanical advantage, it will depend on how the pulleys are connected. In this case, the k probably equals 5, but one would have to look at it. https://www.khanacademy.org/science/physics/work-and-energy/mechanical-advantage/v/...

*March 16, 2017*

**physics**

see other post.

*March 16, 2017*

**physics**

http://www.wikihow.com/Calculate-Terminal-Velocity

*March 16, 2017*

**Science**

I will be happy to critique your response.

*March 16, 2017*

**math**

this makes no sense to me.

*March 16, 2017*

**chemISTRY**

v_rms = sqrt(3RT/M) where M is the 28 for N2, and 4 for He

*March 15, 2017*

**Math**

50/125=xxxx xxx=2*25/(5*25)=2/5=.4=40 percent

*March 15, 2017*

**math**

180=.75*P P=180/.75=240

*March 15, 2017*

**MATH**

you need the bases first. draw the sketch. label the top base a, the bottom c. now notice on c, it is longer than a by 2*k, where k is the length of the base below end triangles. Pyth: (c-k)^2=25^2-15^2 or c-k=20cm but c=a+2K Now the median length: median=(a+c)/2=(c-2k+c)/2 =...

*March 15, 2017*

**AP Physics**

frictionless? think on the spool, would it rotate? it has a force on it (either above the cg or below, I dont have a picture), but would it rotate? I suspect your teacher wants you to consider a mimimal friction...

*March 15, 2017*

**World History**

C is a good answer, however, I would have wished ethnic hate would have been listed. Austria-Hungary had just annexed Bosnia-Herzegovin provinces a few years earlier against the wishes of neighboring Serbia, which likewise coveted them. Ferdinand believed the Serbs to be “...

*March 15, 2017*

**Science**

acceleration=changebelocty/time= 145.08/4.48 m/s^2

*March 15, 2017*

**Maths**

a liter is a dm^3 v=(d/2)^2PI*h=3.5^2*PI m^3 v=3.5^2 *PI (10dm)^3 because 1m=10dm v=3.5^2*Pi *1000liters

*March 14, 2017*

**Physics ( oscillations and waves)**

f*lambda=speed lambda=2*60=1.20m speed=30*1.20 m/s

*March 14, 2017*

**answer!**

The height h thru which it will fall is H=11.50(1-cos39) 1/2mv^2=mgh v=sqrt(2gh) exclamations points are to me a bit exaggerated.

*March 14, 2017*

**physics**

force=k*x=60N/m *.016m

*March 13, 2017*

**physics**

f=kx=230N/m * .08m

*March 13, 2017*

**Physics**

RE=1/2 *I w^2=.5*v^2/r^2 But I=2/5 mr^2 so TE/Re= (1/2 mv^2)/(Mr^2*v^2/5)=2.5 check

*March 13, 2017*

**Physics**

from 15mi/hr to /???????

*March 12, 2017*

**English**

This practice could help to find cures for the illnesses as well as animals. >> Makes no sense. What illnesses? How is it good for the animals? were they sick?

*March 12, 2017*

**math**

Have you studied the Least Integer Function (sometimes called a step function)? https://www.khanacademy.org/math/algebra/algebra-functions/piecewise-functions/e/evaluate-step-functions-from-their-graph

*March 11, 2017*

**Math**

L=W+16 P=2L+2w=2(W+16)+2W=4W+32 4W=200-32 W=168/4=42 L=58

*March 11, 2017*

**math**

what is 7*5? Think about that. That is the smallest whole number. But the smallest number you can multiply A and get a perfect square is = 1/(5^3*7^3*3^2) multiplying it then will leave you with A'=9, a perfect square. i am not certain your teacher was thinking of that, ...

*March 11, 2017*

**Science**

depends on what you mean by chemical and biological. Some hold that biological is inherently chemical.. and, depends on what you mean by great thrust: Much effort is aiming for breakthrus in the biological area, especially in genetic engineering. But honestly, those are just ...

*March 11, 2017*

**Science**

power=I^2*R dp=2IR*dI dp=2di * RI so the increment in dp is 2Percent

*March 11, 2017*

**physics**

one wonders where the charges are.

*March 10, 2017*

**physics**

What is coulomb's law? Do you have a question on it?

*March 10, 2017*

**PRe calc story problem!!**

story problem? Calculus is not elementary school. Q(t)=Qo*ekt 25=100*e12k ln of both sides... ln(1/4)=12k -1.38629436=k*12 solve for k then, for half life... .5=ek*t solve for t (take ln of both sides) thalf=ln(.5)/k

*March 10, 2017*

**Electricity and Magnetism**

Tangental accelertation? the magnet field put a force on the electron perpendicular to the electron path. So If I am understanding the question correctly, the tangential acceleration is zero, as the tangential velocity is not changing.

*March 10, 2017*

**Science**

bp was elevated?

*March 10, 2017*

**Social Studies**

D. The Muslim nations had traded with the far East for centuries, and those goods became commonplace in Europe. AFter the muslims were driven off, the desire for those goods remained

*March 9, 2017*

**physics**

I will be happy to critique your thinking or work on this.

*March 9, 2017*

**physics**

Use conservation of momentum to solve this.

*March 9, 2017*

**English**

c and e

*March 9, 2017*

**physics**

Look up the moment of inertia for a disk, and the sphere. flywheel(disk)=Ifly*w sphere=Isphere*ws set them equal, solve for ws put radii in meters...

*March 8, 2017*

**physics**

momentum is conserved initial momentum=finalmomentum 2/5 *M*6.96E8wi=2/3*M*6.37E6*wf wi=1rev/25days wf=wi*(6.96E8/6.37E6) = about 4 revs/day or 27.46rad/day

*March 8, 2017*

**Algebra**

It is prime, cannot be factored in the real number system

*March 8, 2017*

**science**

the hydrogen attached to the -O- in the OH is the detachable H

*March 8, 2017*