If Q = 25 $\mu$C, q = 10 $\mu$C, and L = 40 cm in the figure, what is the magnitude of the electrostatic force on q?
A)28 N
B)22 N
C)20 N
D)14 N
E)10 N

Question

If Q = 25 $\mu$C, q = 10 $\mu$C, and L = 40 cm in the figure, what is the magnitude of the electrostatic force on q? 
A)28 N 
B)22 N 
C)20 N 
D)14 N 
E)10 N

Quizplus · Accepted Answer

We can use Coulomb's Law: $F=\frac{kQq}{r^2}$ where $k$ is the Coulomb constant, $Q$ and $q$ are the charges and $r$ is the distance between them.

First we need to find the distance between the charges. By the Pythagorean theorem, we have:

$r=\sqrt{L^2+d^2}$

where $d$ is the vertical distance between the charges. From the figure we can see that $d=20$ cm. Substituting:

$r=\sqrt{(0.4	ext{ m})^2+(0.2	ext{ m})^2}=0.447	ext{ m}$

Substituting this and the given values of $Q$ and $q$:

$F=\frac{(9	imes10^9	ext{ N}\cdot	ext{m}^2/	ext{C}^2)(25	ext{ }\mu	ext{C})(10	ext{ }\mu	ext{C})}{(0.447	ext{ m})^2}=20.0	ext{ N}$

Therefore, the magnitude of the electrostatic force on $q$ is 20 N. The closest answer choice is C: 20 N.

If Q = 25 μ\muμ C, Q = 10 μ\muμ C, and L = 40 Cm in the Figure, What

If Q = 25 $\mu$ C, Q = 10 $\mu$ C, and L = 40 Cm in the Figure, What