# Search results

1. ### Passed my exams. Thank you all!

Dear all, I officially passed all of my exams yesterday. It seemed very unlikely but now I get to study physics and hopefully pursue my childhood dreams. I want to really thank you. I quit my job and was on a budget so that I couldn't afford tutoring, but I don't think I would have been able to...
2. ### Find the speed of a copper loop falling in a magnetic field

Hi all, so I had this problem and on the exam and I got a solution but I had an mass-term in there which wasn't given. I used Farraday's Law of Induction to get the Voltage induced. Then I used ##rho* \frac{A}{4a} ## for the resistance and divided the Voltage by that to get the current. I then...
3. ### Set up the differential equation showing the voltage V(t) for this RC circuit

Hi all. I have another exam question that I am not so sure about. I've solved similar problems in textbooks but I have a feeling once again that the correct way to solve this problem is much simpler and eluding me. Especially because my answer to a) is already the solution to c) and d) (I did...
4. ### What is the rotational acceleration of a falling chimney?

Hi all, I found this problem in a new textbook I'm working through. And my energy conservation equation was ## mg\frac {h}{2} = \frac {1}{2} I ω^2 + mg \frac {h}{2}*sin(55) ## My solution was wrong and after checking why I found that they used cos(35) as the angle. The rest was the same. I'm a...
5. ### Changing the Air Temperature with a hair dryer

Hi, so I found this on another old "AP" High School Finals Exam. I think I may be super lost. Because the only way that I can think about is KE = 3/2kT. And then that the difference of the Kinetic Energy of the air Particles is the Q supplied by the heater inside the air dryer. So ## \frac...
6. ### Force on a copper loop entering into a magnetic Field B with speed v

Hi, second problem in one evening, I'm sorry! But i'm also not quite sure if I did this one right. I had thought I need lenz's law but there is no current before entering the field so I just use the induced Voltage? My approach: ## V = \frac {B*A}{t} ## ## IR = \frac {B*A}{t} ## and ## A = v*t...
7. ### Spring is stretched, then attached to a mass, what is its speed at x?

Dear all, I am back with another Spring problem. I have tried to use the insights I gained from your help last time: https://www.physicsforums.com/threads/find-v-x-of-a-mass-suspended-from-a-spring.972942/page-3#post-6190934 I figured I start with calculating the new equilibrium by ## x...
8. ### Pendulum's Tension using Force reasoning and Newtons 3rd Law.

Hi, I have a conceptual question. I was doing some problems on pendulums and found something that confused me. I attached a drawing. I used to always solve these problems by using some trigonometry and trying to find the Tension. i.e. ## m*g = F (of the Tension) * cos(theta) ## so ## \frac...
9. ### Find the charge of a mass hanging from a pendulum in an electric field

Hi, so I was able to solve this problem by just equating the forces (Tension, mg, and EQ). But I thought I could also solve this problem with Conservation of Energy. However, I calculated it several times, and I never get the right answer this way. Doesn't the Electric Field do the work to put...
10. ### Classical Textbook or other resource with comprehensive challenging problems?

Hi all, can you recommend a textbook or other resource with comprehensive (meaning spanning multiple subjects) and challenging physics problems and also the solutions? I have already worked through Giancoli (no-calculus), Ohanian (calc based) and the two dummies workbooks. I have been working...
11. ### With what speed does the tip of a 25 meter high tree hit the ground?

Hi, I am still working on the same exams problems, the second last one is giving me a bit of a headache after I found this https://physics.stackexchange.com/questions/2372/how-long-would-it-take-for-an-upright-rigid-body-to-fall-to-the-ground which contradicts my solution. Can I assume that when...
12. ### Find v(x) of a mass suspended from a spring

Hi all, I have a problem that I've been grappling with for the past 2 hours. I was confident at first that I found the correct solution, but when I tried to verify I didn't have a constant in my v(x) function. Here is my attempt: I appreciate your help kind internet strangers!
13. ### Pendulum Conservation of Energy

Hi, I have a general question to pendulums. I hope it is ok to post it in this format. Please accept my apologies for my poor English. Homework Statement : As a general Example: I have a Pendulum of length L with Angle Theta as maximum displacement. I know how to solve these problems. Find...
14. ### Is Walter Lewins Loop Trick. Correct or False?

Homework Statement I posted this in the advanced section, but glancing over the problems there I realized this probably belongs here.[/B] Hello everyone. I hope this is the right category. I am in desperate need of help. I have no High School Education. But a few weeks ago I participated in an...