Ball suspended in a horizontal electric field

[cdriscoll]

A table tennis ball of mass 10g carries a charge of 0.04 micro Coulombs. It is suspended at the end of a rine threa 25cm long and placed in a horiztonal electric field. The effect of the field is to move the ball's centre 1.5cm to on side of a vertical line through the point of suspension.

What is the force on the tennis ball?

What is the magnitutde of the electric field?


I'm not even sure how to start this one so any help would be really appreciated!

 

[grzz]

What is the formula for the electric force on a charge q due to an electric field E?

 

[cdriscoll]

F= k q(1) q(2) / d^2 ?

 

[SammyS]

F= k q(1) q(2) / d^2 ?

That's the magnitude of the force one charge exerts on another.

The question asked by grzz was

"What is the formula for the electric force on a charge q due to an electric field E? "

 

[cdriscoll]

E=F/q ?

 

[SammyS]

E=F/q ?

Good enough.

How much is the force of gravity, which is downward. ?

 

[cdriscoll]

9.8m/s/s...?

I'm really sorry I've been taking ages to reply I am so busy, but my assignment is due tomorrow so I'm screwed anyways... thanks for trying sorry I am so bad at physics :( if you still want to try and explain though that would be good i just might be slow replying, school starts tomorrow

 

[grzz]

Now check whether the gravitational force is negligible compared with the electric force.

 

[SammyS]

9.8m/s/s...?

I'm really sorry I've been taking ages to reply I am so busy, but my assignment is due tomorrow so I'm screwed anyways... thanks for trying sorry I am so bad at physics :( if you still want to try and explain though that would be good i just might be slow replying, school starts tomorrow

That's the acceleration due to gravity, g. The force due to gravity is the weight = mg .

The force due to gravity (the weight) is downward. You are given the mass, so you can calculate this.

The electric field is horizontal, so is the electric force.

The tension in the fine thread must cancel both of these. The tension (also a force) is along the same direction as the thread.

 

[grzz]

Now check whether the gravitational force is negligible compared with the electric force.

I am revising my one suggestion.

The weight CANNOT be negligible because the weight must balance the vertical component of the tension.

 

[grzz]

A diagram IS ALWAYS HELPFUL.

Try finding the components of the weight in the verical and in the horizontal.