Vector analysis homework question

[chemboy]

3 electrons q1, q2, q3 setup in a right angled triangle

q1
|\
| \
q3-q2

charges are

q1 = +2.5 X 10^-17C
q2 = +3.0 X 10^-17C
q3 = +3.5 X 10^-17C

distances between the charges
q1-q3 = .03 m
q1-q2 = .05 m

setup FBD

\
\ 2F1
\
/
/ 3F1
q1

2F1 = k*q1*q2 / .05^2
= 2.7 X 10^-21N
3F1 = k*q3*q1 / .03^2
= 8.75 X 10^-21N

now I think I use cosine law to figure this out

Fnet = 2F1^2 + 3F1^2 - 2(2F1)(3F1)cos45

is this going the right direction, or did I screw up my FBD

 

[chemboy]

find the magnitude and direction of the force acting on q1

 

[Quisquis]

Homework forums are https://www.physicsforums.com/forumdisplay.php?f=152" way.

 

[tiny-tim]

now I think I use cosine law to figure this out

Fnet = 2F1^2 + 3F1^2 - 2(2F1)(3F1)cos45

is this going the right direction, or did I screw up my FBD

Hi chemboy!

erm … where did 45º come from?

And are you sure that minus should be there?

 

[berkeman]

Thread moved to Homework Help forums.