Question with large number???electron charge?


by graphicer89
Tags: charge, numberelectron
graphicer89
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#1
Jul31-09, 10:34 PM
P: 55
1. The problem statement, all variables and given/known data

The electric charge of an electron is -1.6 x 10^-19 C. What is the force exerted between two electrons separated by one meter? Is it attractive or repulsive?

2. Relevant equations

F= K Q1Q2 / D^2

3. The attempt at a solution

Im horrible with large numbers and especially at negative exponents....so this is a guess

K = 9x 10^9 N x m^2/c^2

Q1 = -1.6 x 10^-19 C
Q2 = -1.6 x 10^-19 C
D= 1 m


F= 9 x 10 ^9 N x m^2 X ( -1.6x 10 ^-19 C x -1.6x 10 ^-19 C / 1^2 m)

F= 9 x 10 ^9 N x m X (3.2 x 10^19 C^2 )
F= 28.8 x 10^28 NxmxC^2.....is the answer i got....

I know i am completely off but how can i do this ...this is basically math but im just not with well large numbers...
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rl.bhat
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#2
Jul31-09, 10:43 PM
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F= 9 x 10 ^9 N x m X (3.2 x 10^19 C^2 )
This step is wrong. -1.6x10^-19 X -1.6x10^-19 = ?
graphicer89
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Jul31-09, 11:06 PM
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Quote Quote by rl.bhat View Post
F= 9 x 10 ^9 N x m X (2.56 x 10^19 C^2 )
This step is wrong. -1.6x10^-19 X -1.6x10^-19 = ?
Thats the thing i dont know...do you add the exponents together??

2.56 x 10^-38????

1.6 x 1.6 = 2.56 but what about the 10^-19? do i add them or does it stay the same????

Actually now i got 2.6 x 10 ^-38...by multiplying both

rl.bhat
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#4
Aug1-09, 03:41 AM
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Question with large number???electron charge?


Quote Quote by graphicer89 View Post
Thats the thing i dont know...do you add the exponents together??

2.56 x 10^-38????


Actually now i got 2.6 x 10 ^-38...by multiplying both
This is correct.
Redbelly98
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#5
Aug1-09, 09:03 AM
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Quote Quote by graphicer89 View Post
Thats the thing i dont know...do you add the exponents together??
Yes, you add the exponents when you are multiplying two numbers.

Do you have a calculator that you can double-check things like this? If not, Google can be used as a calculator:

http://www.google.com/#hl=en&q=1.6e-...fp=MyO-rnw0Pu0

Note the computer-standard "e-19" to signify "10-19 "
graphicer89
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#6
Aug1-09, 10:58 AM
P: 55
Quote Quote by rl.bhat View Post
This is correct.
Ok so after i have 2.6 x 10^-38 is it C^2?
graphicer89
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#7
Aug1-09, 11:04 AM
P: 55
Well let me put what i have..... F=9 x 10^9 N x m^2/c^2 X( 2.6 x 10^-38 c^2 /1 m^2)

that is what i have...do i cancel out the m^2 and c^2? from both sides? so that only the N is remaining?
rl.bhat
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Aug1-09, 11:07 AM
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Quote Quote by graphicer89 View Post
Well let me put what i have..... F=9 x 10^9 N x m^2/c^2 X( 2.6 x 10^-38 c^2 /1 m^2)

that is what i have...do i cancel out the m^2 and c^2? from both sides? so that only the N is remaining?
Yes. Force should be in N.
graphicer89
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#9
Aug1-09, 11:11 AM
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Quote Quote by rl.bhat View Post
Yes. Force should be in N.
Cool so if i did my calculations right....i got 2.3 x 10^-28 N am i close or am i really off? but i think this force is repulsive no??? because its a positive number .......or is it attractive?
rl.bhat
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#10
Aug1-09, 11:39 AM
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Quote Quote by graphicer89 View Post
Cool so if i did my calculations right....i got 2.3 x 10^-28 N am i close or am i really off? but i think this force is repulsive no??? because its a positive number .......or is it attractive?
Like charges repel each other.
Redbelly98
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#11
Aug1-09, 01:28 PM
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Quote Quote by rl.bhat View Post
Like charges repel each other.
Exactly. The equation gives the magnitude of the force. Use the opposites attract / likes repel rule to figure out the direction.


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