What magnitude charge creates a 4.17 N/C electric field at 9.78 m?

[BuBbLeS01]

Simple electric field problem...

Homework Statement

What magnitude charge creates a 4.17 N/C electric field at a point 9.78 m away?

Homework Equations

The Attempt at a Solution

E = (k * Q) / r^2
Q = (E * r^2) / K = 4.43 x 10^10 C
Why isn't that right?

 

[hage567]

Check your math. I don't get the same answer with the expression you used.

 

[BuBbLeS01]

oh shoot I was using K = 9 x 10^-9 because everything is in nC so that's what I did...thanks!

 

[BuBbLeS01]

Is this question not asking the same thing?

The electric field 4.1 cm from a small object points toward the object with a strength of 199400 N/C. What is the object's charge?

q = 3.72 x 10^-8 C

 

[hage567]

Is this question not asking the same thing?

The electric field 4.1 cm from a small object points toward the object with a strength of 199400 N/C. What is the object's charge?

q = 3.72 x 10^-8 C

If the field is pointing towards the charge, what does that tell you about the charge?

 

[BuBbLeS01]

its negative

 

[hage567]

Right. I don't see anything wrong with your calculation otherwise.

 

[BuBbLeS01]

thanks so much!