Physics help
Well today i bombed my physics test on electric potential, and a few questions really stumped me xD. I know it's kind of a silly thing to ask basil for answers but my parents can't answer them and neither can my friends D:. I don't know if the problems are just difficult or i'm just dumb. :c anyways i have the answers but i'm just looking for work to get to those answers. Any help would be appreciated. Sorry if i'm offending anyone .-.
1. The absolute potential at the cneter of a square is 3.0 V when a charge of +Q is located at one of the square's corners. What is the absolute potential at the square's center when a second charge of -Q is placed at one of the remaining corners? [b] A:Zero [/b]
2. A uniform electric field with a magnitude of 500 V/m, is directed parallel to the +x axis. If the potential at x= 5.0m is 2500V, what is the potential at x=2.0m?[b] A:4000V [/b]
3. A proton moves 0.10m along the direction of an electric field of 3.0 V/m. What is the change in kinetic energy of the proton? [b] A:4.8 x10^-20J [/b]
4. Two parallel plates, seperated by 0.20m, are connected to a 12-V battery. An electron realeased from rest at a location 0.10m from the negative plate. When the electron arrives at a distance of 0.050m from the positive plate, what is the speed of the electron? [b] A: 1.0x10^6 m/s[/b]
5. How much work does 9.0 V do in moving 8.5x10^18 electrons? [b] A: 12J [/b]
Again if i'm offending someone in anyway i'm sorry, but i'm really lost x-x
9 Comments • Newest first
@Food You should be my physics tutor!
Electricity was always my worst subject in physics, I can't really help.
Thanks guys it means a lot ^^
1.
V = kq/r
When you find electric potential the sign (+/-) of the charge matters.
So if k(+Q)/r in the center of the square is 3V, then K(-Q)/r is -3V at the center of the square.
The r's are equal because no matter what corner the charges are they will be have the same distance from the square's center.
Now just add up the electric potentials at the center -3V + 3V = 0V.
3. A proton moves 0.10m along the direction of an electric field of 3.0 V/m. What is the change in kinetic energy of the proton? A:4.8 x10^-20J
err so far I only know number 3.
We know that E(elec field intesity) = Fe/q.
Therefore Eq=Fe.
3.0 V/m * (1.6*10^-19) = 4.8* 10 ^-19 N
Multiply: Fe*d= Wdone
(4.8*10^ -19) * (0.1) = 4.8*10^-20 J
4.
E = V/d
E = 12V/0.2m = 60 V/m
V = Ed = (60 V/m) * (0.1m - 0.05m) = 3.0 V
W = qV = 3.0V * (1.6*10^-19) = 4.9 * 10^-19 J
qV = 0.5mv^2 :
4.9 * 10^-19 J = 0.5(9.11*10^-31 kg)(v^2)
v = 1.02*10^6 m/s
5.How much work does 9.0 V do in moving 8.5x10^18 electrons? A: 12J
W = |q|V
Total charge(q) = multiply # of electrons by the charge of each electron
q = 8.5x10^18 electrons(1.6*10^-19) = 1.36 C
1.36 C * 9.0V = 12.24 J
2, 3, and 5 seem like questions that you can solve with equations. I'm not entirely sure because I've already forgotten everything from physics, but it's worth looking through a formula sheet.
#2. X = 5.0 meters (GIVEN)
5m + (difference in this case is 5m - 2m = 3m) = 8m
Go back to the 500 V/m and multiply by 8m to cancel out "m" would yield 4000V your answer ^^
No no i didnt mean that haha. Last time i did one of these threads people started commenting on me offending them
Oh god, Physics was one hell of a subject
Good luck!
How the hell are you offending people? idgi man. Kids these days.
I'm still at the heat/thermal energy chapter so idk yo.