Electric charges, wrong answer D: ?

[Eats Dirt]

Homework Statement

Find the net force at point A

q1=-6x10^-5 C
q2=-3x10^-5 C

q1 is 3m north of A
q2 is 3m east of A



find the net force on a -1.2x10^-5 C charge

The Attempt at a Solution

first off I find how the electric field is with no charge at point A

= 6.7 x 10^4 N/C [E 63 degrees N]

= Fe= qE
Fe= (-1.2x10^-5)(6.7x10^4)
Fe= 0.804 [W 63 degrees S]

However the answer in the book says the answer is 8x10^4 N [W63degreesS]

i don't know if it is me or the book making the mistake?

 

[PeterO]

Homework Statement

Find the net force at point A

q1=-6x10^-5 C
q2=-3x10^-5 C

q1 is 3m north of A
q2 is 3m east of A
find the net force on a -1.2x10^-5 C charge

The Attempt at a Solution

first off I find how the electric field is with no charge at point A

= 6.7 x 10^4 N/C [E 63 degrees N]

= Fe= qE
Fe= (-1.2x10^-5)(6.7x10^4)
Fe= 0.804 [W 63 degrees S]

However the answer in the book says the answer is 8x10^4 N [W63degreesS]

i don't know if it is me or the book making the mistake?

Read carefully to make sure the distances really are 3m. That is a long way away.
Your calculation look OK to me, given the figures you have provided here. But to 3 figures that should be 0.805 [0.804984]
Given that some of the data was given to only 1 significant figure - you answer should have been 0.8

Peter