Recent content by twinklestar10

but how to prove it using mathematical calculations? i couldn't get it as 0 using the integration of electric field with respect to r.

Homework Statement An outer shell of charge +Q is insulated by a light thread. There is an inner sphere inside which is earthed. The radii of the outer shell and inner sphere are b and a respectively. What is the potential of a point which is at a distance r from the centre of the inner...

Actually, I just saw your reply after I posted my last reply... Anyway, so I now understand the problem I encountered before, the key is that I didn't realize there was a third force besides tension, provided by the rod. and that exactly can cancel the weight when the mass is at a height of...

actually i have an idea... do you think that the motor would also provide a force directing up (static friction between the rod and the mass?!) in order to move the mass? that means there are 3 forces, tension, weight & this upward force then i can conclude that the vector sum can be 100%...

But it seems not to agree with the free body diagram --- tension + weight, how can I get the vector sum as a centripetal one?

they claim that... in the case when the mass is at a height of r the net force shouldn't be 100% centripetal, but it is at a small angle to the horizontal, say pointing towards 8 o'clock (please forgive my poor English...) because there are 2 forces acting on it: weight & tension I...

but there is no tangential acceleration as the speed is uniform, so only centripetal acceleration exists... that means total acceleration is actually centripetal acceleration, by F=ma, net force should be centripetal too, isn't it? how come the correct answer isn't like that?

Homework Statement An object of mass m is attached to a light rod of length r which is driven by a motor at a steady rate. The object performs uniform vertical circular motion. Centripetal force is provided by tension and weight. Draw the net force acting on the mass when the mass is at a...