Electric field and acceleration

[ENCgirl]

Homework Statement

During a thunderstorm the electric field at a certain point in the Earth's atmosphere is 1.07e5 N/C, directed upward. Find the acceleration of a small piece of ice of mass 1.09e-4 g, carrying a charge of 1.08e-11 C.

Homework Equations

F= (q')(E)

a= F/mass

The Attempt at a Solution

F= (1.08 e -11 C) ( 1.07 e 5 N/C) = 1.16 e-6 N

a= F/m= (1.16 e -6)/ (1.09 e -7 kg)= 1.06 e-2 m/s^2

The above answer is what I get but the key is saying:

0.802 m/s^2


Please help me figure out what I am doing wrong.
Thank you.

Thanks again to anyone who replies. It is late here so I am signing off.. I will reply tomorrow if anyone has responded.

 

[gneill]

Have you accounted for all the forces?

 

[ENCgirl]

Have you accounted for all the forces?

I am not sure. I thought so because I followed the example in the book.

 

[gneill]

What other force do you think would be operating on a particle of mass 1.09e-4 grams?

 

[ENCgirl]

What other force do you think would be operating on a particle of mass 1.09e-4 grams?

hmmm. Gravity? :) Wow! I think the lightbulb just came one.. :)

 

[ENCgirl]

What other force do you think would be operating on a particle of mass 1.09e-4 grams?

So, would I take the force that is listed in the problem and add the force of gravity on the object that I solve for then take the cumulative of the two ans use that as the F in the a= F/m formula?

 

[gneill]

So, would I take the force that is listed in the problem and add the force of gravity on the object that I solve for then take the cumulative of the two ans use that as the F in the a= F/m formula?

That's the general idea. Pay attention to the directions of the forces.

 

[ENCgirl]

That's the general idea. Pay attention to the directions of the forces.

Thanks!