# Search results

1. ### Special Relativity - Help Please!

The 7 years is as measured by the traveling twin's frame. So my intuition wants to say that his return is 14 years in his frame. However I think that this may be flawed due to lorentz contraction of the distance being traveled.
2. ### Special Relativity - Help Please!

Homework Statement Two twins start their clocks at the same time, one of them travels for 7 years at a speed of 4/5c, reverses direction and returns at half the speed. The other twin remains stationary, what is the difference in their age? Homework Equations t = t_p γ The Attempt...
3. ### Whether the boy can catch the ship? relative velocity

Direction should affect your time traveled by the boy, and thus your velocity of the boat. Maybe you found a way the angles cancel out to an identity? I'm not sure I'm just considering the problem in my head.
4. ### Shopping Carts, Finding Horizontal Force

This problem is easier if you rotate your axis 13 degrees. So draw the x axis to be parallel with the acceleration. With your current axis ... Fx = F and don't forget your normal force and force due to gravity. Now, if you redraw your axis along the direction of acceleration Fx = Fcos(13)...
5. ### Whether the boy can catch the ship? relative velocity

Hmmm, since it doesnt say anything about the boy's direction when he starts swimming I assume they want you to consider a right triangle...of course this depends on your level of physics class also... if you find this is not the case then use the law of cosines to solve the problem . Consider a...
6. ### Non-Uniform Dielectric

Thank you tim!
7. ### Non-Uniform Dielectric

This isn't a homework problem, just something to explore my understanding so correct me if any of my assumptions are wrong. I have given myself the situation where I have a capacitor of area "A" and separation "d" Between them is a non-uniform but continuous dielectric, so that the...
8. ### Capacitors, energy storage and energy release

Just a short concept question for understanding... I understand that a capacitor stores a charge, However I'm told that capacitors can be used to store up a charge and release it very quickly. How does this energy get released is what I don't understand. To my understanding of a...
9. ### Work problem 2

What is work? Work=\int F ds From this you can find that Work=-\Delta U and Work=\Delta KE Read your book about work and energy.
10. ### Quick Couple Concept Questions on Guass's Law

Thanks a bunch ehild!
11. ### Spring pushing block down and up hill problem

I haven't checked for myself if your numerical answer is correct or not. Don't think of any picture in energy problems to be necessarily to scale, think of h as a changing variable, so it could easily stretch way up or even stretch below the point you call h=0. It might help you in other...
12. ### Spring pushing block down and up hill problem

No, not JUST spring potential. But you must include spring potential. You start out not moving, you don't have any kinetic energy initially. The question says after the block runs into the second spring it compresses 2.1 m before being shot out the other way. So your final kinetic energy is...
13. ### Work problem 2

what's making the paratrooper fall? Force by gravity. So to stop him what force must be applied? Think of newtons third law. What is work? work is force times distance. The distance is the depth of the crater, what is the work?
14. ### Work problem

I think your equations may be confusing you. For instance what is h? h or (d) should be the distance that the cyclist is traveling. so h=d sin (6) make sense? now W = -\Delta U so if you call your initial position h=0 your final potential is mgh now can you use d to solve for velocity?
15. ### Spring pushing block down and up hill problem

Well you should know that KE_{i} + U_{i} = KE_{f} + U_{f} This is equivalent to saying that energy is conserved. So Kinetic Energy initial + potential energy initial is equal to Kinetic Energy Final + Potential Final. A spring is just potential energy. Energy is stored in the spring...
16. ### Quick Couple Concept Questions on Guass's Law

Just a couple quick questions I was wondering about. Also, this is an Introductory E&M class so we don't actually perform the surface integral so knowing \oint\vec{E}d\vec{A}=EA=\frac{q_{enclosed}}{\epsilon_{0}} When using cylindrical symmetry I'm supposed to ignore any flux on the top and...
17. ### Finding E field from potential

Thank you rl.bhat I took a look at the lamba again and figured out I should have simply just solved for lamba instead of q using my potential integration. Thanks!
18. ### Finding E field from potential

Well I can't possibly answer with that solution though. I know nothing about the length of the cylinder except that it is very long. To answer in terms of lamba would be an incomplete answer since I still have unknown variables.
19. ### Finding E field from potential

Two long conducting cylindrical shells are coaxial and have radii of 20 mm and 80 mm. The electric potential of the inner conductor, with respect to the outer conductor, is +600V. In the situation provided, an electron is in circular motion around the inner cylinder in an orbit of 30mm...
20. ### What happends when we oscillate three pendulums next to each other?

well more correctly it's gravitational potential to kinetic energy, but you have the right idea.
21. ### What happends when we oscillate three pendulums next to each other?

They might start out at a different oscilation periods, but a forced oscillation will quickly take over if that would happen. In which the system will resonate and oscillate all together about the center of mass.
22. ### SHM/Spring Concept Questions

Thank you so much, this helped clear a lot of things up for me.
23. ### What happends when we oscillate three pendulums next to each other?

you don't use equations? well the pendulum will simply start oscillating at a specific angular frequency. It won't necessarily oscillate like a simple pendulum however. There's a different moment of inertia and center of mass. Without using equations, I'd say average out the distances apart to...
24. ### SHM/Spring Concept Questions

Just going through some concept questions and these three have me stumped. If anyone can lend a hand. If a uniform spring is cut in half, what is the force constant of each half? Justify your answer. How would the frequency of SHM using a half-spring difer from that using the same mass and...
25. ### Newton's Cradle, Simple Harmonic Motion

Is it possible to see newton's cradle in simple harmonic motion? Im thinking that the period is the same as a simple pendulum, if not how would I calculate this?
26. ### Angular Momentum In A Helicopter

Ok so here's my thought L(Helicopter)=I(rotor)*Omega(rotor) taking the derivative with respect to time on each side I get Torque=I*alpha(rotor) So F*R=I*alpha So F=(I*alpha)/R is that correct?
27. ### Angular Momentum In A Helicopter

Those are dual rotor helicopters, which have several varieties of how they can be aligned. However single rotor helicopters traditionally use the description above. I did a little bit of wiki-research before I considered the physics. http://en.wikipedia.org/wiki/Helicopter_rotor The...
28. ### Angular Momentum In A Helicopter

So we have a helicopter with a blade that has the moment of inertia "I" that is "2R" long and is spinning at an angular velocity \omega. To stabilize the aircraft, the tail ruder must exert an equal an opposite force. Can someone point me in the direction of how to calculate the force...
29. ### Torque and angular accelerationfinding coeff. of friction

Don't worry about it, angular momentum can be a hard concept but I recommend working hard at it. It will come a lot in physics from now on =)
30. ### Simple Net Gravitation problem

Thank you so much for your reply. I totally neglected that the net force would have superposition. Thanks again