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[Jack04]

Why are colours created when various salts such as LiCL(s) are lit by flames? Is it because of the heat generated makes the electron jump to another energylevel(shell) which again releases photons?

It is related to the binding energy between the molecules which are being broken down.

Someone solve this please:
x(3x + 4y)= 2x(2y + 4y)

(3x + 4y) = 2(6y) (dividing through by x)
3x = 12y - 4y
3x = 8y
y = (3/8)x

edse was correct.

[Nikitn]

Why are colours created when various salts such as LiCL(s) are lit by flames? Is it because of the heat generated makes the electron jump to another energylevel(shell) which again releases photons?

Yes, except the photon is released when the electron falls from a higher orbital. Different substances will burn with different colours once set on fire.

[The Norseman]

Hey some physics questions! Oh and thanks for the help

1. A car increases its speed from 10 m/s to 18 m/s on a 80 m long runway. The acceleration is constant. How high was the speed of the car once it had reached half way? aka once it had reached 40 m.

Can someone show me the formula I have to use and how to solve it?

2. A man is skiing down a 13,0 meter long slope within 4,0 seconds. The initial velocity is 0 and the acceleration is constant. Find the velocity at the bottom of the slope.

[Jack04]

http://en.wikipedia.org/wiki/Equatio...m_acceleration

[Nikitn]

Are you expecting us to solve this for you? Assignments such as these you can solve by reading your book and then applying the learned knowledge.

Trust me, it's for the best.

[The Norseman]

I had read the book and did not find any examples similar to the questions stated above, but I figured it out afterwards.

[chriscase]

I had read the book and did not find any examples similar to the questions stated above, but I figured it out afterwards.

Good job!

Test problems will be harder, so the more you practice, the better.

[The Norseman]

Hey I have an assignment which I have been struggling with!

A motorcycle starts and has in the beginning an acceleration of 3,0 m/s^2 for 5,0 seconds. After that the acceleration is 2,0 m/s^2 for 3,0 seconds.
a) what is the Velocity in the end of the "trip" Here I simply did this (3,0 * 5,0) + (3,0 * 2,0) = 21m/s and it was the correct answer. I mean can I really do that? Or must I use some formula for it?
B) How far has the motorcycle driven after 8,0 seconds have passed. This is where I am kind of stuck. I do have A, T, V and Vo, but I can not seem to get the formulas working properly... I know I have to find the S for both the 3,0m/s^2 length and the 2,0m/s^2 length and then add them together. Oh I must just use S=1/2at^2 for the first one! so 37,5 metres. Aaaand for the second one it does have a Vo which is 15 m/s ? and then just finish the formula I think...

So now I have 37,5 and 54 metres and now I only have to add them together and KABLAM there is the answer! Now the only thing which remains is to draw the damn thing, which I suck at...

[Sphere]

If you want a visual way of doing it, graph the velocity vs. time. The distance traveled at any given time is just the area below the graph at that time. So 8 seconds would look like this ...



Which gives you the same answer.

No need to memorize formula's besides the area of a triangle and the area of a rectangle. Once you get to calculus you'll learn how add up the area under the graph even for squiggly lines that cannot be broken down into common shapes.

[The Norseman]

Wow thanks for the help! I really appreciate it! +rep!

[The Norseman]

The main problem I am experiencing is that I do not always know what they want me to find! like in this task:

You throw a ball straight up into the air with a startingspeed of 9,0m/s. g= 9,81m/s^2

a) What is the speed in the toppoint? Answer: 0
b) How high does the ball come? Vo-gt=0 t=Vo/g = 9,0/9,81 = 0,92 s. Then I find S by using S=VoT-0,5gt^2= 9,0m/s*0,92s-0,5*9,81*0,92^2= 4,13 = 4,1
c) By which times is the ball 3,0 metres over the original/beginning point? This is where I struggle to use the different formulas. I have no idea what formula they want me to use.. Must I make some graph or derivate something?

[John Doe]

c) By which times is the ball 3,0 metres over the original/beginning point? This is where I struggle to use the different formulas. I have no idea what formula they want me to use.. Must I make some graph or derivate something?

it happens twice (way up and down), so there should be at²+bt+c=0 equation to solve.

3meter = 0.5 g t² + v₀ t + x₀

[VALIS]

I hate to waste peoples time but can someone watch this video
http://www.youtube.com/watch?v=ysVcAYo7UPI
Skip to 3:00

And please explain i4 to me? Sal clearly says i x -i is 1. Okay. But then he jumps to -1, but where on earth does he conjure up -1 from, and then he says (i)x(i), well where the hell is he getting i x i from? I don't understnd where or how he jumped to that, it doesn't seem to follow from what he's saying.

ing i, I hate it so much.

[Jack04]

I hate to waste peoples time but can someone watch this video
http://www.youtube.com/watch?v=ysVcAYo7UPI
Skip to 3:00

And please explain i4 to me? Sal clearly says i x -i is 1. Okay. But then he jumps to -1, but where on earth does he conjure up -1 from, and then he says (i)x(i), well where the hell is he getting i x i from? I don't understnd where or how he jumped to that, it doesn't seem to follow from what he's saying.

ing i, I hate it so much.

i² is defined as -1. That is what it is. It doesn't need to be calculated.

[VALIS]

i² is defined as -1. That is what it is. It doesn't need to be calculated.

I know that i2 is -1. I guess i4 is just i2 times i2. I was just a bit perplexed where he was coming from with that approach.

[Sphere]

And please explain i4 to me? Sal clearly says i x -i is 1. Okay. But then he jumps to -1, but where on earth does he conjure up -1 from, and then he says (i)x(i), well where the hell is he getting i x i from? I don't understnd where or how he jumped to that, it doesn't seem to follow from what he's saying.

-a = (-1)a

That is all he did in that step and where the -1 comes from.

i(-i) = (-1)(i)(i)

[Blaze86420]

Organic chemistry question I had on a test: Which statement explains why iodoacetic acid is weaker than fluoroacetic acid?

a)C-I bond is longer than C-F
b)The anion of fluoroacetic acid can be stabilized by resonance
c)Fluorine is more electron withdrawing than iodine
d)Radius of iodine atom is bigger than fluorine atom
e)Two oxygens in fluoroacetic acid have two different hybridizations

I picked c), here's my reasoning:

Can't be a) because both bonds are single bonds therefore, same length.
Can't be c) because both anions resonate.
Can't be d) because a larger radius (polarizability) only matters when the H donated is bonded to that atom (F and I)
Can't be e) because the oxygens have identical hybridization (sp2 bond)

So it's c), because Fluorine is more electronegative than Iodine, therefore, stabilizes the anion (conjugate base) better.

[Alkaline Earth]

I know that the more electrons withdrawn from the vicinity of the carboxyl carbon, the stronger the acid. So what you said is the right answer, I believe anyways.

[Alkaline Earth]

Alright I haven't asked for help here since I was in Algebra 1 last year, I'm now in Geometry and am stumped on a homework question.

Was able to make a picture of the question pretty easily.

[Nikitn]

a) The student in question assumes angle CAB is 60 degrees without having any information to suggest that's the situation.
b) Just draw a triangle which doesn't have identical angles (like one triangle with one 90 and one 70 degree angle) to disprove the student's reasoning.