Physics Questions Help!

1. Sep 14, 2013

NasuSama

1. The problem statement, all variables and given/known data

Two point charges are distance d = 47.8 cm apart, They have equal and opposite charge, each with magnitude Q = 1.62 μC. The negative charge is on the left, and the positive charge is on the right. An electron (mass $9.11\times 10^{-31}$ kg, charge $1.6\times 10^{-19}$ C) is placed half-way between the charges.

c) What is the force of the electron?

d) What is the direction of the force on the electron?

2. Relevant equations

• $E = \dfrac{kQ}{r^2}$
• $F = Eq$

3. The attempt at a solution

I just want to make sure if I'm right for both parts of the problem

For part (c), I got this

$E = \dfrac{2kQ}{(\frac{d}{2})^2}$

$F = Eq$
$F = \dfrac{2kQq}{(\frac{d}{2})^2}$

where

$d = \text{distance between the two charges before the electron is placed}$
$q = \text{charge of the electron}$
$Q = \text{point charge with given value}$

By substitution, I got $8.17 \times 10^{-14}$ N.

For part (d), I believe the answer is "right, toward the positive charge" since electron attracts with the point charge with positive sign.

2. Sep 14, 2013

PhysicsandSuch

Looks good to me: I didn't check your calculator skill, but the physics seems right.