Recent content by funoras

it should be at the center of the sphere i guess ? in that case the potential at any point on the sphere will be q/4πε_0d , as expected edit: didn't see that article you posted. it helped a lot. thanks! The rest is piece of cake.

Yes, i know how to solve this problem using method of images if the sphere is grounded. The induced charge would be q_i=-qr/l. But in this case there is no charge induced,since the sphere is not grounded, the charges just move inside the sphere, but the net charge still remains zero.

Homework Statement Find the attractive force between a neturally charged metal ball of radius r and a point charge q, located a distance l from the center of the ball. Also find the work needed to move the charge to infinity. The ball is not grounded. Homework Equations - The...

Thank you for the wonderful idea. So i have calculated each voltage drop U_1=q_a/C=6U/11 U_2=q_a/2C=3U/11 U_3=q_a/3C=2U/11 now after the reversion, we should have U-U_3+U_2-U_1=q_b C_a and from here q_b=36CU/121 q_b is the additional charge you were talking about. Now for each of...

Homework Statement Three capacitors, of capacitances C , 2C and 3C respectively are connected in this order in series to a voltage U battery. After they are charged, the middle capacitor (2C) is disconnected and then connected back again with reversed polarity. Find the charges on each of the...

Homework Statement In an infinitely large evenly charged dielectric cylinder(charge density is \rho ) there is an infinitely large cylindrical void. Prove that the electric field inside the void is homogenous and find its value. (picture) http://img513.imageshack.us/img513/5747/61734727.png...

Thanks for your feedback. Yes, the volume did in fact decrease. Maybe you're right , the pressure isn't constant, i can't find another explanation. But in that case there isn't enough data to solve this problem. If i assume that all the water vapor dissociated, then why is the volume change...

Homework Statement In a closed vessel there was some water vapor. After the water vapor dissociated, the temperature decreased by 10%, and the volume by 20%. Find the change in internal energy. (U{initial}-U{final})/U{initial} Homework Equations The Attempt at a Solution Let's...

Homework Statement An ice ball is melting in a water bath. Find the time needed for the ice ball to completely melt. Heat transfer is only due to heat conduction. The radius of the ball is R_0=1cm. The temperature of the water in the bath is t=10°. There is an infinite amount of water...

Okay so this is my solution T is the tension force , and i'll assume g=10m/s^2 For the 1st pulley 2T_1=Mg+m_1 g+F_f so T_1=50,75N 2nd pulley 2T_2=T_1+m_2 g +F_f T_2=26,625N 3rd pulley 2T_3=T_2+m_3 g +F_f T_3=15,0625N and the 4th pulley it should like something like this i guess...

Yeah that makes sense . So it should be something like this. By the way,about the 4th pulley, since it is fixed (it doesn't move) , shouldn't i ignore it's mass ? http://img204.imageshack.us/img204/3059/unledme.jpg Uploaded with ImageShack.us

The system is going up with some constant speed. and i drew all the friction forces in blue. Can you tell me is this corrent ? http://img202.imageshack.us/img202/3059/unledme.jpg Uploaded with ImageShack.us

Homework Statement An object of mass M=10kg is being pulled up by a system of pulleys. a)What force do you need to exert on point A for the object to move uniformly ? b) What force do you need to exert on point A, if the friction in each of the pullies is 0,5N and the pulleys are not massless -...

It's not a textbook problem. However, thanks a lot for your help ! :)

So mg sin \alpha - F = ma FR=mR^2\beta/2 a=\beta R and from here a=2gsin\alpha /3 and i can find the translational velocity, but what about the angular velocity? it seems i will need the radius, which is not given