# Recent Activity

1. ### Christian Hoermann liked JBA's post in the thread Optimum Wheel Radius for a Terrestrial Robot.

Note: The real US weight given is 110 lbs and 110 lb weight = 49.9 kg force not kg mass, as I understand it. But apart from the...

Aug 23, 2017 at 6:42 PM
2. ### phinds replied to the thread B What is the process for developing new physical laws?.

No, not right. Sure they work in their own domains but the fact that they DON'T work in the other's domain means they are in some way...

Aug 23, 2017 at 6:41 PM
3. ### stoomart liked mfb's post in the thread B Dark matter variations on Earth.

Dark matter didn't form a rotating disk like the regular matter. It is more like a big cloud of gas with dark matter particles moving...

Aug 23, 2017 at 6:40 PM
4. ### stoomart liked Drakkith's post in the thread B Dark matter variations on Earth.

No, he means that dark matter falls into the Sun and passes right through, emerging on the other side with the same speed that it...

Aug 23, 2017 at 6:38 PM
5. ### haruspex replied to the thread Find friction coefficient given initial and final velocity?.

What equations for motion under constant acceleration have you been taught?

Aug 23, 2017 at 6:34 PM
6. ### scottdave replied to the thread Find friction coefficient given initial and final velocity?.

Welcome to PhysicsForums. If you have not already, please take a moment to read over the rules, especially the part about how the...

Aug 23, 2017 at 6:33 PM
7. ### tim9000 attached a file to the thread Calculating the mutual coupling coefficient of E cores.

Thanks Jim, Yes, if you either halve the volts/turn or double the area of the core, B is halved. I found this: [ATTACH] Which gives a...

Aug 23, 2017 at 6:32 PM
8. ### NascentOxygen liked jedishrfu's post in the thread buying a second-hand laptop.

If it's discovered to be stolen, there's no document that will help you keep it. A receipt may give some leeway with the police as to...

Aug 23, 2017 at 6:24 PM
9. ### RockyMarciano replied to the thread I Gravitational time dilation, proper time and spacetime interval.

This is then an essential difference from riemannian spaces. In the latter unique geodesics between distant points also imply constant...

Aug 23, 2017 at 6:24 PM
10. ### BillTre liked Janus's post in the thread My science Field trip.

As those of you who followed the Eclipse thread likely know, I went to Lincoln City OR to catch the solar eclipse. We arrived early...

Aug 23, 2017 at 6:21 PM
11. ### samalkhaiat replied to the thread A U(1) invariance of classical electromagnetism.

Mathematically, it makes no difference what so ever, if you replace my 3-form j by “their” ~^*\!J. However, it is economical and more...

Aug 23, 2017 at 6:19 PM
12. tyger2020 posted a new thread.

### Find friction coefficient given initial and final velocity?

I am not sure how to approach a problem involving the friction coefficient when only given initial velocity, final velocity, and...

#### Forum: Introductory Physics Homework

Aug 23, 2017 at 6:11 PM
13. ### rude man replied to the thread Third Order High Pass Filter (Report).

Butterworth is not necessarily montonically non-increasing with frequency (for a low-pass). whereas Bessel is. I considered Butterworth...

Aug 23, 2017 at 6:11 PM
14. ### OmCheeto liked David_777's post in the thread Stargazing 2017 eclipse photos.

[ATTACH] About 10:18am Monday August 21, 2017 from Riverfront Park within a large crowd in Salem, Oregon at the totality exit stage....

Aug 23, 2017 at 6:04 PM
15. ### David_777 attached a file to the thread Stargazing 2017 eclipse photos.

[ATTACH] About 10:18am Monday August 21, 2017 from Riverfront Park within a large crowd in Salem, Oregon at the totality exit stage....

Aug 23, 2017 at 6:02 PM