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1. ### Calculating Deuterium Atoms in 4 kg Ocean Water and Energy Needs of US

a little confused i tried the first part but I'm not sure if this is what you meant... molecular weight of water = 18 g/mol = .018 kg/mol then: 2(.018kg/mol) = .036 hydrogen atoms in 1 kg of water 4kg(.036) = .144 hydrogen atoms in 4 kg of water .00015(.144) = 2.16e-15 number of...
2. ### Calculating Deuterium Atoms in 4 kg Ocean Water and Energy Needs of US

this is homework problem I'm having some trouble with... i haven't had chemistry yet so I'm not sure how i could convert atoms into kg, and the textbook i have doesn't do any examples of problems like this one... i don't even know where to begin. Deuterium (A=2, Z=1) is an attractive fuel for...
3. ### Faraday's law of electomagnetic induction

ok i think i finally understand how to find R now... R= .027 once i figured that out, i did: I=emf/R = (-708)/.027 = -26266.1 P=I(emf) = (-26266.1)(-708) = 18596420.37W E=Pt = (18596420.37W)(.45s) = 8368389.167J and that should give me the electrical energy dissipated in the wire right...
4. ### The electric generator

thanks guys... you really helped me
5. ### Faraday's law of electomagnetic induction

won't that give me units of ohm/m^2 ? i thought i was supposed to be getting rid of the m's because the R is in units of ohm... i'm still very confused about this problem.
6. ### The electric generator

The coil of a generator has a radius of 0.14 m. When this coil is unwound, the wire from which it is made has a length of 5.4 m. The magnetic field of the generator is 0.10 T, and the coil rotates at an angular speed of 35 rad/s. What is the peak emf of this generator? so i have: r= .14m L=...
7. ### Faraday's law of electomagnetic induction

A piece of copper wire is formed into a single circular loop of radius 13 cm. A magnetic field is oriented parallel to the normal to the loop, and it increases from 0 to 0.60 T in a time of 0.45 s. The wire has a resistance per unit length of 3.3 x 10-2 ohm/m. What is the average electrical...
8. ### Parallel Plate Capacitors

so it would be like this? mass + k|q1||q2|/r^2\sin = E + mg/cos ? which would give me... (6.70e-3)((((8.99e9)(150000)q2)/(r^2))/sin 30) = (8.436)(.0758)? i would be solving for q2 right? but what about r^2, what would i make that? -annie
9. ### Parallel Plate Capacitors

A small plastic ball of mass 6.70×10-3 kg and charge +.0150 uC is suspended from an insulating thread and hangs between the plates of a capacitor. The ball is in equilibrium, with the thread making an angle of 30.0° with respect to the vertical. The area of each plate is 0.0200 m^2. What is the...
10. ### Magnitude of net electric field

ahha i figured it out... :)
11. ### Magnitude of net electric field

this is what i tried ((8.99e9)(2.2e-12))/((3.0e-2)^2) and i got 21.976... so now am i supposed to multiply by 4? cause that answer i got isn't right -annie
12. ### Magnitude of net electric field

Four point charges have the same magnitude of 2.2 10-12 C and are fixed to the corners of a square that is 3.0 cm on a side. Three of the charges are positive and one is negative. Determine the magnitude of the net electric field that exists at the center of the square. i tried using...
13. ### Ball in gravity: how high does the ball go? Initial velocity?

you guys are awsome thanks so much... i understand what i was doing wrong now, i just didn't understand holly's explanation correctly... we've never learned that gravity could be anything besides 9.81. :)
14. ### Ball in gravity: how high does the ball go? Initial velocity?

whouldn't it just be easier if i took the derivative of this: h(t)=5.9+69t-16t^2 so: h(t)'=69-32t but what do i do from here to get the max height? our physics teacher has only taught us using formulas...
15. ### Ball in gravity: how high does the ball go? Initial velocity?

ok so i understand why i shouldn't included gravity in this but how else can i solve for t?? i think I'm making this much harder than it should be, but i never learned anything about kinematics...
16. ### Homework assignment on optimization

for question one i did: f(A)'=3-(3800000/A^2) A=1125.46 is this shortest side? i wasn't sure where to go from here for the second question i have: f(w)'=3.04-(1380/w^2) and w=21.306 so then i put the 21.306 into the original equation l=460/w=460/21.306=21.590 at this point I'm not...
17. ### Ball in gravity: how high does the ball go? Initial velocity?

i have learned derivatives but i was trying to learn how using the formula... i now understand how to get the initial velocity and height ( i didn't know they gave then to me like that), but I'm a little stuck on the max height... this is the work i did: 0 = v0 * t - 1/2 gt^2 0 =...
18. ### Homework assignment on optimization

hi i have two homework assignment I'm kinda stuck on they are very similar i was hoping someone could help me... 1) A rancher wants to fence in an area of 1,900,000 square feet in a rectangular field and then divide it in half with a fence down the middle parallel to one side. What is the...
19. ### Ball in gravity: how high does the ball go? Initial velocity?

i know this is a really simple problem but I'm kinda stuck on it since i don't know what to do with the equation I'm given :eek: ... Having won the game, a baseball pitcher hurls the ball up in the air. Its height in feet t seconds after the throw is given by h(t)=5.9+69t-16t^2 How high...
20. ### :eek: standing waves where to begin

i think i got the answer using the equation f' = ((v + vo)/(v- vs))*f which is the same as the equation f'=(1+u/v)f since in my case the source isn't moving... i was wondering if someone could check this for me to see if i was right... i have 3.3Hz=(1+u/(343m/s))438Hz which when i multiply it...
21. ### :eek: standing waves where to begin

any help would me much appreciated... the assignment is due tonight thanks :)
22. ### :eek: standing waves where to begin

beat frequency we are just starting beats now but my homework assignment is due sunday night, which is the day before the lecture on standing waves and beats...so far I've been reading and understand that 3.3Hz are the beats per second which is the beat frequency... and i probably need to use...
23. ### :eek: standing waves where to begin

Two loudspeakers face each other, vibrate in phase, and produce identical 438-Hz tones. A listener walks from one speaker toward the other at a constant speed and hears the loudness change (loud-soft-loud) at a frequency of 3.3 Hz. The speed of sound is 343 m/s. What is the walking speed?