# Search results

1. ### Lens maker's equation used correctly?

Homework Statement An object is placed 60 cm from a thick double convex lens, with faces of radii of curvature 20 cm and 30 cm, with thickness of 2 cm, and index of refraction is 1.5. Find the position of the image...
2. ### Difference between two wave functions?

4. a) A certain string has a linear mass density of 0.25 kg/m and is stretched with a tension of 25 N. One end is given a sinusoidal motion with frequency 5 Hz and amplitude 0.01m. At time t=0, the end has zero displacement and is moving in the positive y-direction. Find the wave speed...
3. ### Difference between two wave functions?

I just started studying this stuff but on a couple occasions my answer was a different sign than the teacher's answer key, so I used the wrong function. This is what confuses me, how to know which to use in order to get the right sign. In the question, an end of a string is given sinusoidal...
4. ### Difference between two wave functions?

Hi, I'm looking through my teacher's notes and he says that a wave function for a sinusoidal wave can be written: y = A sin (ω t – k x) or y = A sin (k x - ω t) The textbook gives it in the second form. I think that using one over the other gives the same answer but in the opposite sign. I...
5. ### Finding electric field via a given potential

Ok I am also getting 3472.8 but I'm getting positive because it's: E = -kc((x/x+L) - ln|x+L| + 1 + ln|x|) which gives -kc(-.19) which is 3472.8?
6. ### Finding electric field via a given potential

If V = kc (integral) (x)dx/(d+x) then shouldn't E = -dV/dx where dV/dx just equals (d/dx)(kc (integral) (x)dx/(d+x)) which equals (kc(x))/(d+x) so E = -(kc)(1/2) = -8.99 x 10^3 N/C ?
7. ### Finding electric field via a given potential

Yes it is a rather badly worded problem... But yes, from my discussion with other students, we placed the rod's extreme left end at the origin. I wish I could show my work but I have it on paper and this is the last thing I have not done for this 5 problem assignment. I will have to pick one...
8. ### Finding electric field via a given potential

I've just spent time with another student with this problem and we're really lost because we've got 4 different answers from different sources and not one of them are the same. We've gotten 8.99 x 10^3 N/C, -3.47 x 10^3, -1.45 x 10^4 N/C, and 4.225 x 10^4 N/C from the above poster. Can anyone...
9. ### Finding electric field via a given potential

I've done all my work on paper and I ended up with E(x) = -kc[ln(L-x) + x/(L-x) -1 -ln|x|] where x = -d where d is 1m. It's been a couple days but I plugged in my numbers and got 1.45 x 10^4 N/C. But this is a positive answer, shouldn't the electric field be to the left/negative?
10. ### Finding electric field via a given potential

If I differentiate that with respect to d, I get that E = -(-3472) N/C which means that it is positive. But shouldn't it be negative?
11. ### Finding electric field via a given potential

Homework Statement The plastic rod of the length L=1 m has a non-uniform charge density λ=cx where positive constant c =2x10^-6 [some unit]. What unit c has to have? Find the electric potential at the point on the x axis 1 m to the left from the left end of the rod. Find the electric field at...
12. ### Finding electric field via potential

I would like to know if either: -3.47 x 10^3 N/C or -1.45 x 10^4 N/C Are correct. Thank you :)
13. ### Finding electric field via potential

Homework Statement The plastic rod of the length L=1 m has a non-uniform charge density λ=cx where positive constant c =2x10^-6 [some unit]. What unit c has to have? Find the electric potential at the point on the x axis 1 m to the left from the left end of the rod. Find the electric...
14. ### Can you clarify this step (charge density and integrals).

Hi, if you have the book: Physics for Scientists and Engineers 8E, Serway Jewett On page 675 (Chapter 23), Example 23.8 there is a step taken during the integration I don't understand: How do you go from "2r dr" in the numerator to d(r^2)? If there is info or link to the property of...
15. ### For those who have this textbook.

Yeah it's actually labeled μ in the book
16. ### For those who have this textbook.

I found it online: http://www.cramster.com/answers-sep-10/physics/blocks-masses-m1-m2-nbsptwo-blocks-masses-m1-m2-table_950775.aspx The answer key gives: b) F, c) F - P, d) P, e) m1: F - P = m1a; m2: P = m2a I want to add that obviously in the book the coefficients are labeled "mu"1 and 2
17. ### For those who have this textbook.

Homework Statement In Physics for Scientists and Engineers Volume 1 Eighth Edition (Serway, Jewett) Number 55. in Chapter 5, I checked the answer key and would like to know why they don't consider the forces of friction in a), b), c), d), and e)? This confuses me. Thank you. Homework...

Thanks :)
19. ### How to define change of angular momentum in non-isolated system?

Ok that makes sense. If the ball were coming from the right side would we add mvL instead, because the momentum being added to the system is in the same direction of its initial angular momentum?
20. ### How to define change of angular momentum in non-isolated system?

Homework Statement http://tycho.physics.wisc.edu/courses/phys201/fall06/Discussion/Disc14Solution.pdf [Broken] problem 38, part b) Homework Equations I final w final = I initial w initial The Attempt at a Solution I understand that the snowball is introducing a net torque and I know that...
21. ### Understanding about differentials?

Homework Statement Problem 7.29: http://cas.umkc.edu/physics/wrobel/phy240/Homework%20%205.pdf Homework Equations dr= R d(theta) The Attempt at a Solution I don't understand how to get R d(theta) = dr from the last part of the question, any explanation about how it works is...
22. ### Solving without using differentiation?

Wow ok thank you for that information about cubic degrees and their relation to constant acceleration, I will stick to my derivative answer but I was just curious as to other types of solutions because I know that many students in the class have not completed their differential calculus seeing...
23. ### Solving without using differentiation?

Well I plugged in my new values for initial position and got 46.9 N but I don't think that's the right answer. 19 m = -1 m + 0 + (1/2)ax(t^2) ax = 10 m/s^2 26 m = 2 m + 0 + (1/2)ay(t^2) ay = 12 m/s^2 so Fx = (3.00 kg)(10 m/s^2) = 30 N and Fy = (3.00 kg)(12 m/s^2) = 36 N Ft =...
24. ### Solving without using differentiation?

I guess I assumed that the initial velocity was zero because plugging t=0 into the derivative of the equations would get you 0 from the velocities? I used differentiation to come to that conclusion. Oh wait a second, I guess the initial positions wouldn't be zero since plugging t = 0 would...
25. ### Solving without using differentiation?

Homework Statement Hi all, I'm trying to understand why my second way of solving this problem doesn't work: A 3.00kg object is moving in a plane, with its x and y coordinates given by x= 5t^2–1 and y=3t^3 + 2, where x and y are in meters and t is in seconds. Find the magnitude of the net...
26. ### Using mass of copper in both air and liquid to find density of liquid?

I did the calculations and the only problem is that it seemed TOO simple haha. I got .90 gm/cm^3 which sounds a lot more reasonable! Thanks again!
27. ### Using mass of copper in both air and liquid to find density of liquid?

Wow that is very very interesting. Unfortunately this is one of my physics lab questions and the physics lab we are taking is completely separate from the physics course itself so the topics covered by our professor are not related strongly to the labs. For example I have no idea about the...
28. ### Using mass of copper in both air and liquid to find density of liquid?

I calculated the volume of the copper based on its density and air weight: V = 180 gm/(8.93gm/cm^3) = 20.2 cm^3 Used that volume and the submerged weight: d = 162gm/20.2 cm^3 = 8.02 gm/cm^3 I don't think I did it right because I'm not familiar with the physics of the situation but I'm trying...
29. ### Using mass of copper in both air and liquid to find density of liquid?

I also found it to be rather high but I have not encountered such a problem, any tips as to how to understand this question is appreciated :)
30. ### Using mass of copper in both air and liquid to find density of liquid?

1. A piece of copper whose density is 8.93 gm/cm^3 weighs 180 gm in air and 162 gm when submerged in a certain liquid. What is the density of the liquid? 2. d = m/v 3. I wasn't sure how to compute this but I calculated the volume of the copper based on its density and air weight...