Physics 12.3.4c - Electric Field Example Problems

[louisvl10]

Thank you!! Very helpful

[gujli1]

youtube.com/user/93Rekay

[MiXtApEMesSiAh22]

Hey for the second problem could you have used the F=Kq1q2\r^2?

[nichtmuttersprachler]

There's another way to do the last problem. Use the kinematic equation (final velocity)^2 = (initial velocity)^2 + 2ad. We're given initial and final velocity, so we just need to rewrite the acceleration term to solve for displacement. Since F = ma and since the force of this electric field is F = -eE, we can rewrite acceleration as a = (-eE)/m. Now, just plug this acceleration into the original kinematics equation, isolate the displacement variable, plug in the actual numbers, and solve.

[derekowens]

@nichtmuttersprachler Yes, that is a very good approach. Sometimes there are two, or more, ways to solve a given problem. And of course they should all give the same answer.

[feenokhan]

You are a Godsend. 

[nhellin]

how did u get 1.6x10^19 ?



[derekowens]

@nhellin  That's the charge on an electron (or on a proton). It's one of the fundamental constants in the universe.

[backyardbeachbum]

thanks man. you're a life saver



[derekowens]

@utprospect 0.001 and .001 are equivalent. Either one should work fine on most calculators

[jeproxwild]

where did he get the 9x10^9 Nm^2/C^2 ??

[jeproxwild]

@jeproxwild i see, i get it, its just a constant value

[derekowens]

@jeproxwild Yes, that's the electrostatic constant, one of the fundamental constants of the universe.

[manikangpapel05]

you make more sense than the boring physics book and the even more boring teacher... Thank you very much

[MP265]

One word: genius.

[XxStopherLixX]

u saved my physics grade.

[16justanna]

Thank you !

[animefreak619240]

my brain is being blasted. this is the first time im doing this. i'll return tomorrow... and the day after.... until i get these down.

[MythicalSun]

Thanks for the help.

[JonnyA2006]

In my scool we have been taught E=Q/4PIE times epsolon times r^2 is this still right?

[lifeson30]

@JonnyA2006

Yes. Since 1/(4*pi*eps) is a constant, you can clump into a single parameter - "K" in the video. You do this for a few reasons: to make the expression less cumbersome and easier to look at, and to highlight the important variables - your variables Q and r, which will vary from problem to problem. By contrast, K=1/(4*pi*eps) always has the same value, no matter what the problem is.

[freighter014]

OMFG finals are tomorrow and it's 12:00 am in the morning right now and these videos are gonna save my butt thank you so much i owe you my high school career

[nformby]

I noticed that I was useless at questions like this while revising. Thanks to this awesome tutorial, I'm now able to do all similar questions on my past papers!

I hope you know that you are really helping many people with their exams, I really appreciate it!

[lilmaqi]

id kill to have a teacher like you.

[stradivary02]

i think something is missing in the problem no.1's answer, the problem is asking about the direction and the magnitude.... the answer must have direction, so the answer must be E=(kQ/r^2) r hat.... thus, it would be (2.16x10^9)sin(angle) j hat..... if the angle is 90degress, it would be 2.16x10^9 j hat... j hat is the direction of the electric field.....

[chickenleon]

really helpful vids, keep up the good work!

[franko04133]

WOW ur videos are awesome !! keep it up!

[1006Will]

DUDE, YOU ARE THE MAN....THXXXXXXXXX!!

[muntas1]

I tried solving the final problem by using the acceleration formula v(final squared) - v(initial squared) = 2*a*s and somehow got 1.65 * 10(-9) :D

[anevmann]

Second part of the second task i get 6.84 * 10 ^-2 = 0.0684

So its probably a typo in your case.

Great video, i've learned this alot better from you than my current teacher :D

[infernalcreation666]

I learnt more from this video than I have learn in the entire topic in school. Thank you so much!!!!!

[fatslug888]

you are a god. i love your videos. thank you very much

[Nenyong166]

thx!!!

[robcorpus]

sir thanks it helps me a lot

[EDDIEDELROSARIO09]

thanks

[fabregassed]

how do find the time to put all these up? thanks they're amazing little videos, great if you have a little doubt or are completely stuck, i live in the uk and am doing my a-levels, even though this is for people in the US, physics doesnt change :).

[derekowens]

Yes, physics and math is universal. Even the Little Green Men in the Andromeda galaxy use the same equations we do.

I've been making these videos for my students since 2005.  Last count I had over 4700 of them! I'm just putting some of the better ones up YouTube. Bringing them here has been a lot of fun.

[Swetlana0]

Hey!

I think you should upload all 5000 as many of us in other parts of the world aren't able to access all of these videos (full version) cuz it is not practical to take the plan u offfer.

[kaziabir1]

Is a 10th grader supposed to understand these problems? because I do, although I'm not familiar with these formulas, we just started the basics.

[derekowens]

Yes! This is high school level physics, and the course I have put together is appropriate for anyone who has had Algebra 1. So if you can do the math, and can understand the physics concepts that I have explained, then these problems should make sense.

[afcweswarrior]

This was helpful.

[weskerq80]

you are great. really good teaching :)

[antcastonguay]

In the last problem, could you have done it with F = ma, (acceleration), and then solve for distance in a kinematic equation ?

[derekowens]

Yes, you certainly could, and you should get the exact same answer. Many situation in physics can be approached using either the kinematics equations or energy equations.

[yasenbg1988]

Thanks a lot. Very helpful !