Register to reply

Question with large number?electron charge?

by graphicer89
Tags: charge, numberelectron
Share this thread:
graphicer89
#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...
Phys.Org News Partner Science news on Phys.org
Hoverbike drone project for air transport takes off
Earlier Stone Age artifacts found in Northern Cape of South Africa
Study reveals new characteristics of complex oxide surfaces
rl.bhat
#2
Jul31-09, 10:43 PM
HW Helper
P: 4,439
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
#3
Jul31-09, 11:06 PM
P: 55
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
#4
Aug1-09, 03:41 AM
HW Helper
P: 4,439
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
#5
Aug1-09, 09:03 AM
Mentor
Redbelly98's Avatar
P: 12,064
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
#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
#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
#8
Aug1-09, 11:07 AM
HW Helper
P: 4,439
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
#9
Aug1-09, 11:11 AM
P: 55
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
#10
Aug1-09, 11:39 AM
HW Helper
P: 4,439
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
#11
Aug1-09, 01:28 PM
Mentor
Redbelly98's Avatar
P: 12,064
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.


Register to reply

Related Discussions
Number Theory: Calculating mod large number Calculus & Beyond Homework 9
Large number Calculus & Beyond Homework 4
Is ln(1+exp(x)) = x when x is a large number? General Math 11
Large number... Fun, Photos & Games 3