Recent content by LovePhys

Homework Statement Homework Equations - Charge conservation - Equipotential surfacesThe Attempt at a Solution Let Q1 be the amount of charge on the inner sphere with radius c, and Q2 be the amount of charge on the outer sphere with radius b. Using Gauss's law, I figured out that Q1=+2Q and...

@gneill Thank you. I came up with a different answer now, but it is not 0.5 For cylinder A, the final velocity of the center of mass is still v=\sqrt{gh} For cylinder B, I think that since the surface is frictionless, and all the forces that are acting on it (gravity and normal force...

Homework Statement Homework Equations mgh=\frac{1}{2}mv^2+\frac{1}{2}Iω^2 The Attempt at a Solution I used conservation of energy, and found that the final velocity of the center of mass is independent of the object's mass, so in both cases: v=\sqrt{gh} . Therefore, the ratio is 1. However...

@Doc Al: Thanks for the hint. I think the maximum angular velocity is also the final angular velocity ω=4rad/s, isn't it? α=\frac{Δω}{Δt}=\frac{4}{0.5}=8 (rad/s^2) So finally maximum a=0.05\sqrt{4^4+8^2}≈0.894(m/s^2)

Homework Statement A turntable is rotating at a constant angular velocity of ω = 4.0 rad/s in the direction of a clockwise fashion. There is a ten-cent coin on the turntable, at a distance of 5 cm from the axis of rotation. Consider the time interval during which the turntable is...

@jtbell and physwizard: I understand it now. Thank you very much!

Hello everyone, A friend of mine came up with this question in class and I really do not have a good answer. Suppose you have a convex lens that has been cut in half horizontally and the top half removed. The question is: Will the bottom half of the lens still form an image? I really...

@tiny-tim: Your post has answered my question! I have learned something new, thanks a lot!

@tiny-tim: Thank you, you have been so helpful. Btw, sorry for the late reply, I've been thinking about what you said to make sure that I do understand them! :biggrin: But still, I have a problem with this: In Newtonian mechanics, I've never thought that the normal force could be an...

@tiny-tim: Thank you for your reply. I think I know what you mean. Do we generally identify the direction of all the forces and leave the axle force to the last? Oh, and can you please have a look at this problem for me? It is the same kind of question. I don't understand why they say...

Hello everyone, I came across this problem from my Physics textbook. I do not understand why the direction of the axle force is pointing downward. I think the upper part of the disk is exerting a downward force on the pivot (as it is pulled down by the Earth's gravity), and according...

@voko Yes! Why didn't I think about that? Thanks a lot, I got the correct answer! Now I just let n=1 and then find t. :)

@voko and Andrew Mason Thank you very much. I can easily find angular velocity ω=\frac{2\pi}{T} . Also, since this is uniform circular motion, I then think that θ=ωt , so the angle between radial vectors as a function of time is: \Deltaθ=t(ω_{1}-ω_{2}) . But \Deltaθ=0 only when t=0...

@Andrew Mason Thanks for your reply. Yes, I have found the orbital period for both using the equation T^2=\frac{4\pi^2r^3}{GM} , specifically T1≈5456.053s and T2≈5457.274s. Yet, I still cannot see how this helps...

Homework Statement Two Earth satellites are in parallel orbits with radii 6700 km and 6701 km. One day they pass each other, 1 km apart, along a line radially outward from the earth. How long will it be until they are again 1 km apart? Homework Equations s=r*θ The Attempt at a...