god i am an idiot:

Which of these materials could not be used as an electric insulator?


Sand
Plastic
Wood
Wool
Lead
Glass

is say wool. am i right?


2) A TV satelite dish is designed to receive waves of waavelength 3.1 meters What is the frequency of the waves it broadcasts?

no idea

3) A certain region of space has a uniform electric field of 2.0 N/C. If you put a small sphere of charge 3.4 C in this region, what would the force be on the sphere (in N)?

working on it...

1) Isn't lead a metal? I thought all metals were conductors.

2) Broadcast should be the same as reception, so:
f=s/wl (frequency=speed/wavelength) in Hz

3) ?

i would say lead

answer was lead, i submitted by accident, so now i got 5 new questions. argh.


Radio station WPHY broadcasts at 93.2 MHz (note: "M" = "mega" = x106). What is the wavelength of the waves it broadcasts?

the forumla i have is velocity = frequency*wavelength, but i am not given speed, so I assume speed of light (C) , but idk what C is.

A certain region of space has a uniform electric field of 1.7 N/C. If you put a small sphere of charge 2.3 C in this region, what would the force be on the sphere (in N)?

duh! F=qE, F=2.3*1.7, F=3.91 (i hope, edit: yup :p) got the one above wrong tho :()

why do you not know the speed of light. i just looked at a page and it says: The speed of light in vacuum is exactly 299,792,458 m/s (metres per second)

cause i forgot :)

boy am i glad i am nto a physics major

The electrical force between planets is
a) similar to the gravitational force between them.
b) small beacause planets have very small charges.
c) always attractive.
d) much smaller than the gravitational force between them.
e) very, very large.

i know that compared to gravity, electrical force is much bigger, but idk if planets havea large cahrge or not. i think not.

also, i give up on this type of question

Radio station WPHY broadcasts at 92.0 MHz (note: "M" = "mega" = x106). What is the wavelength of the waves it broadcasts?

Let me pull festerhead in here, he's some radio expert!

i got it figured out, thnx tho! i just realzied i forgot to put the mhz *10^6 in the equation. :rolleyes:

Slightly Outdated
 

Well, good shot at trying to shoot down a physics major on a physics 1 problem, but think of it these 2 ways:

A. You start with Vox in the i direction, and Voy in the j direction. this makes the energies
1/2*m*Vox^2*i*i + 1/2*m*Voy^2*j*j = TE
TE = 1/2*m*(Vox^2 + Voy^2)

now, at the top of the arch, Voy^2 is 0, leaving the only kinetic energy being Vox^2 dependant.

B. You Start with Vo velocity at some angle having an i component of Vox and a j component of Voy, thusly, Vo has a magnitude of (Vox^2 + Voy^2)^(1/2) and a direction on theta = arctan(Voy/Vox) in the holy units of radians. Providing Us with a total energy (TE)

TE=1/2*m*(Vo)^2 = 1/2*m*[(Vox^2 + Voy^2)^(1/2)]^2 or
TE = 1/2*m*(Vox^2 + Voy^2)

Now, to make things infinitely more complex for you, assume an IRF(Innercial Refference Frame that travels to the right (assuming straight right is in the i direction) at Vox. NOW we see this object travel directly up and fall directly back down, starting with 1/2*m*Voy^2 kinetic energy and it'll travel straight up, stop momentarily and fall back down.

I can run through the derivations of an equation for H(t) depending on Voy or Range as a function of Vox and Voy.

s0be

and yes, I realize that energy is a scalar, but that doesn't mean you can't break it up into X and Y contributed energies depending on which directions the displacements and components are.

An electron with a velocity of 0.5 x 10^6 m/s enters a region of space A certain region of space has a uniform magnetic field of 0.9 T What is the radius of the circle the electron makes? The mass of an electron is 9.11 x 10-31 kg.

im working on it. i need a circular motion eqn and idk what else, but im workin on it....
/edit
ok, i am gogin to use F = qvb to get F
F = ma to find a
a= v^2/r to get r
/edit
i got 3.159 e -6
/edit
and holy shit i got it right! :D

When an electron in an atom jumps from a level with energy -5.7 eV to one of energy -7.3 eV, what is the energy of the photon that is emitted?

i haev the equation Ei - Ef = hf, and h = the constant 6.626*10^-34, but idk, because it wants E, so yea.....

/edit

don't mind me. i made it much more difficult than it needed to be.

Physics is Phun!!!

Anyone else taking AP physics now?

im taking regents physics. are you in high school or college?

high school, AP Physics C

well if it is so much fun, help me with this one

the electron in a hydrogen atom jumps from the n = 6 orbit to the n = 3 orbit.
What is the wavelength of the emitted photon in meters?

its not a physics C topic i believe, and if it is we haven't covered that yet. I coulda helped you on all the other problems tyou talked about though :).

well tha tdon't do me no good. I have the equation in my notes, i just cant read my handwriting. :(

i'd have that problem if i took notes :). Mostly just do the problems the teach talks about in my notebook and that's it. No crazy verbatim lectures :D. I'm much too lazy :)

we hardly do anything in physics. my teacher is weird. since school started we've done kinomatics (or something like that) and vectors. whoo! Chemistry was way more fun.

Carbohidrat substitution post:
Psychics is cool!

dlink == brain fart

57g tennis ball falls from height of 1m. what is its velocity upon hitting the ground? assume no air resistance and g=-9.81

hint: v^2 = u^2 + 2as.
Very easy. :p

what is the u^2? I assume s = time, which I don't know.

velocity end = velocity inital +2 (9.81) * s

is it just me or is the 57g irrelevant. i don't remeber mass being in any of the motion equations. so therefore it would be V=at would it not?

s = displacement
Assume u - initial velocity = 0m/s
(There are many methods to solve this is the simplest)

velocity end = velocity initial + 2*9.81*1

ve = 19.62 m/s. thnx :)

wait.....19.62 m/s after falling 3 ft? that doesn't make sence.

would this work:

code:
9.81 m      1 m

-----   =  -----

 1 s        x s

x=0.102 s

fuq it. I foudn this free fall simulator

http://physics.bu.edu/~duffy/java/Freefall2.html

and it clocks the fall @ .4515 seconds and a velocity of a more reasonable 4.4294 m/s, so that will be good enough. this is just need a rough estimate for a attention getter for a speech

Wrong, ve = sqrt(19.62) m/s
Refer to original equation:
V^2 = U^2 + 2as
U = 0
Therefore, V = sqrt(2as)
The simulator is right. Pay attention to working next time.

bah. who sqrts things anymore? :confused: i'm better when I do math on paper, i swear. besides, it's late. :p thanks for your help though! :D

Galileo had the same thought climbing the stairs to the top of the Leaning Tower of Pisa ;)

Mass only becomes relavent if forces are involved, for example if you had to take air resistance into consideration.

UJ