# Search results for query: *

1. ### Finding the E-Field between parallel plates

I have a positive and a negative charged plate running parallel to one another. To find the Electric Field to the left of the plates, I say: E dot dA = Qenclosed / permittivity Then E times 2pi(r) = Qenclosed / Permittivity then E = Qenclosed / 2pi(r) x Permittivity and since Qenclosed...
2. ### Derive Centripetal Force Expression with T^2, m, R

I'm asked to derive the mathematical expression for the erlationship of centripetal force as a function of T, m, and R. I've found, from data, that F=0.615/T^2 = 0.05m = 1/4R how would I bring it all together to form one equation involving T^2, m, and R? Any help, thanks.
3. ### Simple Relative Velocities

Opps, lmao. huge mistake, I totally meant to write 20mi/hr. Anyway. Thanks!
4. ### Simple Relative Velocities

If Car A is going 30mi/hr east, and Car B is going 10mi/hr east. What is the relative velocity of Car A to Car B? Wouldn't this just be Va - Vb = Vrelative? So.. 30mi/hr - 10mi/hr, the answer would be 20mi/hr? Any help, thanks. :smile:
5. ### Average speed

But the problem should not be this easy. Our teacher had said that it's not what you think it is. Therefore, I had come up with this, which doesn't come out to make sense for some reason. Maybe someone could point out why? Average Speed = Distance Traveled / Time it took to travel S1 =...
6. ### Average speed

You move from point 1 to point 2, and then from point 2 back to point1, using the identical path. if your average speed from point 1 to point 2 is S1 and the average speed from point 2 back to point 1 is S2. What's the average speed of the entire trip there and back, in terms of S1 and S2...
7. ### Junior physics homework

Conservation of Momentum. Initial momentum must equal final momentum. Therefore... (mass)x(velocity) = (mass)x(velocity) or... (massA)x(velocityA) + (massB)x(velocityB) ... (massX)x(velocityX) = (massA)x(velocityA) + (massB)x(velocityB) ... (massX)x(velocityX)
8. ### Perpendicular 3Dimensional Vectors

How would you go about finding a perpendicular vector, to two 3 dimensional vectors? One way, I solved is using the cross product of the two vectors. Splitting the i's j's and k's up and solving using a determinent. But, what's another way to do it?
9. ### Young's Modulus for Two Materials connected

awsome, thanks a lot.
10. ### Young's Modulus for Two Materials connected

OK another thing I've thought up is saying... F = Y(delta-Laluminum / L-naught)A and F = Y(delta-Lsteel / L-naught)A since force is equal throughout? Then set the two equations equal to one another, where A cancels out? Can anyone confirm this is a way of doing it?
11. ### Young's Modulus for Two Materials connected

If Aluminum and steel are connected as one rod, and are attached to the wall and is pulled upon. How would the change in length for each material of the rod be calculated? I'm given that the Aluminum section is twice as long as the steel section, and the total change in length of the whole rod...
12. ### Line tangent to an elipse given one point

The ditto the teacher handed out to us was not his. A previous teacher had made it, and people were asking about it today, and for him to help us with it. He put it on the board, looked at it, and said - forget it, omit it. although he said he may give extra points for it solved. Hurkyl - I...
13. ### Line tangent to an elipse given one point

Okay, I'm in Precalculus Honors, and have not learned about Derivatives yet, and this is an extra credit problem. I've gathered that you must find the derative of the curve at the point of tangency, and that is the slope of the line. I'll google some more, but any help?
14. ### Line tangent to an elipse given one point

Write the equations of the tangent lines from (3,0) to x^2 + 2y^2 = 6 Anyone have any idea? I've graphed it but i still have no clue where it's tangent to the elipse.
15. ### Calculating the Kinetic Energy and De Broglie Wavelength of an Ejected Electron

If 15eV photon interacts with a Hydrogen atom at groundstate [-13.6eV], and all 15eV is transferred to the atom. How would the KE of the ejected electron be found? and what is the de Broglie wavelength of the electron? For the Kinetic Energy, i said 15eV = KE + 13.6eV, KE = 1.4eV for the...
16. ### Constant frequency for light waves?

"what is the frequency of red light in the air? What is the frequency of red light in the glass?" is the frequency of a light wave length constant? therefore, the answer would be the same?
17. ### Loop Leaving a B-Field

If there's a loop exiting a B-field, where half of it is in the b-field and half of it is out. How would a potential difference be found in the wire? I said that V = BLv, (where L is the height of the loop, disregarding the width) and found V to be 3v. Although, there is one resistor on the...
18. ### Potential difference between plates in a B-Field?

Awsome, thanks so much.
19. ### Potential difference between plates in a B-Field?

F = Eq = qvB. Therefore E = vB So.. V=Ed = vBd?
20. ### Potential difference between plates in a B-Field?

The question runs me through a series of questions actually, and I think they are all linked somehow. The first one asks what the sign of the charge of the particle is. And the answer I got was Negative, since the B-Field is going INTO the paper, and the velocity is to the right. Therefore...
21. ### Potential difference between plates in a B-Field?

Well I'm given two plates and a B-field. a charge is placed inbetween the two plates and moves paralllel to the two plates until the end, where it then makes a downward circle turn. All the while, the charge is in a B-Field. the distance between the two plates is given the B-field is given...
22. ### Potential difference between plates in a B-Field?

How is potential difference found between two plates in a B-field? Any help is greatly appreciated.
23. ### Equilbrium charge between 2 charges

Yep r = R(1 + (\frac{q_2}{q_1})^{\frac{1}{2}})^{-1} equates to 0.66666. That's what I got too using what I said above. I think it's doing the same thing. Anyway, thanks a lot for the help.
24. ### Equilbrium charge between 2 charges

OHHH wow. Thanks a lot. Ok, so for the net electric field to be 0, kq1 / (1+r)^2 + kq2/(r^2) = 0 Alright so: 1) k's drop out, leaving q1 / (1+r)^2 + q2/(r^2) = 0 2) (6.8x10^-6) / (1+2r+r^2) + (-1.7x10^-6) / (r^2) = 0 - multiply through by (1+2r+r^2)(r^2) 3) (6.8x10^-6)(r^2) +...
25. ### Equilbrium charge between 2 charges

Alright, well. The definition of electric field strength? The amount of force that is pulling or pushing on charges surrounding a charge? E=F/q, so the Electric Field strength would be the Force [kq1q2/r^2] divided by the charge, q. That means, E = kq1 / r^2. Oh, also - Eleectric...
26. ### Equilbrium charge between 2 charges

This makes no sense to me... equation 1) q1/r1 +q2/r2 = 0 equation 2) r1 [distance between equilibrium charge -> q1] = 2(R2) plugging it in just gives me zero. help please, anyone?
27. ### Equilbrium charge between 2 charges

OHhhhh is it: Kq1 / r-from-q1 + kq2 / r-from-q2 = 0 so the K's cancel out leaving: q1 / r1 + q2 / r2 = 0 q1 and q2 are knowns but r1 and r2 are unknowns. how would that be solved? Would it be, kq1qe / r1^2 = kq2qe / r2^2 where q1 = q1 q2 = q2, and qe = equilbrium charge...
28. ### Equilbrium charge between 2 charges

isn't the potential of a charge: kq/r? well q(Vb - Va) = kq(q-initial) / ra - kq(q-initial) / rb but that's for moving a charge from one place to another, right?
29. ### Equilbrium charge between 2 charges

So what I did was: Kq1/(1+r) + Kq2/r = 0, making r =the distance away from q2 outside of the system to be the equilibrium point. so q1 is 1m + r distance away from the point, and q2 = r distance away from the point. K's cancel out, you get: q1/(1+r) + q2/r = 0 Some algebra, turns out r =...
30. ### More Electric Energy questions

I thought W = q(Vb - Va)? Or is that only valid when it's one charge moving from one place to another, and W = qVtotal, when there's more than one charge? And yeah, I think I've fallen behind because I can fully grasp the idea of F=k(q1)(q2) / r^2, and E = F/q, but I don't fully understand...
31. ### More Electric Energy questions

The way to solve this, i tried is by saying F = k(q1)(q2) / r^2. So, the force between the two charges is (9x10^9)(2.6x10^-8)(5.5x10^-8) / (1.4^2). Although, from there I'm not sure where to go because that just solves for the force inbetween the two charges and not the EPE or even more...
32. ### Finding the charge given distance apart + some more

The problem with that was that I had [mg] wrong. For the mass, I used the gram value of the mass instead of the kilogram value.
33. ### Finding the charge given distance apart + some more

I got it. Thank you. I did F = ma = 0. and one sphere = equilibrium, created a right triangle with mg, Tension, and Electrical force. Knowing [mg] and the angles, I solved for the Electrical Force. Then set that = to (k)(2q)(q) / r^2, where r = 0.0523 and k = 9x10^9. q = 1.96 x...
34. ### Finding the charge given distance apart + some more

So finding exactly whether it's both positive or negative can not be done? Also, would my equations look like this? er... would the vectors added be: m1g, m2g, k(2q)(q) / r^2, k(2q)(q) / r^2, T1, and T2? add them as vectors and set them equal to zero and solve for q?
35. ### Finding the charge given distance apart + some more

First, I said that the distance between the two spheres is 0.0523m since you can form a right triangle using 0.5m [50cm] as the hypotonose, and 3 degrees as an angle. and multiplying that answer by 2 giving me the distance between the two spheres. From that I know one sphere = 2q, while the...
36. ### Help on some electric potential energy questions

Can anyone help me with number two please? Any other suggestions? Potential difference between the block's A and B position is 90 correct? since 1/2mv^2 = mgh becomes 1/2v^2 = gh v = 42, g = 9.8, that solves for h = 90. so potential difference = 90? Can anyone tell me if that's...
37. ### Special triangles and Unit Circles HELP

Tan = Sin / Cos. You're given Sin = -4/7 Find Cos. Sin^2 + Cos^2 = 1 (-4/7)^2 + Cos^2 = 1 Cos^2 = 1 - (-4/7)^2 Cos = SQUAREROOT ( 1 - (16/49)) Cos = Squareroot (33 / 49) Cos = Squareroot(33) / 7 [You know squareroot of 49 doesn't = -7, and it = 7, because it's in Quadrent 4, where...
38. ### Special triangles and Unit Circles HELP

Yeah 1/cot = tan = -4 / sqrt33. That's correct.

40. ### Special triangles and Unit Circles HELP

OR you could draw a right triangle, make one angle theta, and put in 4 as the side opposite theta, and 7 as the hypotonose (since Sin = opposite/hypotonose = 4/7 [change -4 to 4 since you can't have a negative length of a side]) Use pythagorem theorm to find that the 3rd side = radical 33...
41. ### Special triangles and Unit Circles HELP

sin(theta) = -4/7, cos(theta) = unknown. but you know: sin^2(theta) + cos^2(theta) = 1 (-4/7)^2 + cos^2(theta) = 1 solve for Cos, and since it's a squareroot you're going to get a positive and negative answer, take the positive answer (since cos's positive in the restrictions given of...
42. ### Sin cos problem finding exact value

(sqrt3/2) * (sqrt3/2) = 3/4 you forgot to multiply the two TWO's. I've done that before, =\.
43. ### Help on some electric potential energy questions

For number 2, I thought it was two situations, one with a charge and another with a mass? When you say qV = 1/2mv^2, that's for the charge - what would the mass equal to? I'm a bit confused, could you explain a little bit more please? (The other two problems I figured out with your...
44. ### Sin cos problem finding exact value

Try this: [tex] sin^2 45 degrees [tex], Sin(45) = radical 2 / 2, so sin^2(45) = 2/4
45. ### Help on some electric potential energy questions

Hey - just asking for some help on some electric potential energy questions. First I used the equation 1/2mv^2 = q(Va-Vb) so v = sqrt (((2)(25000)(q)) / m ) and Va-Vb = W / q, so q = W/(Va-Vb) but then I'm stuck and don't know where to go from there since the mass and the charge (q)...
46. ### Another Electric Field Question

So the question reads: "A small drop of water is suspended motionless in air by a uniform electric field that is directed upward and has a magnitude of 8480 N/C. The mass of the water drop is 3.50 x 10^-9 kg. (a) Is the excess charge on the water drop positive or negative? Why? (b) How many...
47. ### Electric Field question

Thanks for the help everyone.
48. ### Electric Field question

Electric Field question: Two charges are located on the x axis: q1 = +6.0 micro-Coloumbs at x1=+4cm, and q2=+6 micro-coloumbs at x2 = -4cm. Two other charges are located on the y-axis: q3 = +3 micro-Coloumbs at y3=+5cm, and q4 = -8 micro coloumbs at y4 = +7cm. Find the net electric field...
49. ### Giving/Recieving Electrons

Thanks for the response. Ohh okay, so after A and B are touched, it becomes: A=+2q, B=+2q, C=0q then C and A touch, becoming: A=+1q, B=+2q, C=+1q then C and B touch, resulting: A=+1q, B=+1.5q, C=+1.5q Is that how it should be done?
50. ### Giving/Recieving Electrons

The question goes as follows: The correct answers are: (a) +1.5q (b) +4q (c) +4q Although, my logic doesn't seem to give me these answers, I was wondering if anyone can explain why and how to approach this problem. My logic goes as follows: Sphere A = +5q Sphere B = -q Sphere C...