A pith-ball A of mass `9xx10^-5` kg carries a chargeof `+5muc`. What must be the magnitude and sign of the charge on a pith-ball B held 2 cm directly above the pith-ball . A such that the pith-ball. A remains stationary?

A free ptih-ball of 8 g carries a positive charge of 5xx 10^-8 C. What must be the nature and magntiude of charge that should be given to a second pith-ball fixed 5 cm vertically below the former pith-ball so that the upper pith-ball is stationary?

A positively charged glass rod attracts a suspended pith-ball. Does it imply that te pith-ball is negatively charged?

Three point charges of +2muC ,-3muC and -3muC are kept at the vertices A, B and C respectivel of an equilaterla triangle of side 20 cm. What should be the sign and magnitude of the charge to be placed at the mid-point M of side BC, so that the charge at A remains in equilibrium?

Two pith-balls each of mass 5xx10^-4 kg are suspended from the same point by silk threads 0.2 m long equal charges are given to the balls, which separate, until the threads enclose an angle of 30^@ , Calculate the charge on each pith-ball.

A small ball of mass 2 xx 10^-3 kg, having a charge 1 mu C, is suspended by a string of length 0.8 m. Another identical ball having the same charge is kept at the point of suspension. Determine the minimum horizontal velocity that should be imparted to the lower ball so that it can make a complete revolution.

A 5 kg ball is trhown up with a speed of 10 m/s. What is the height to which it rises?

A particle of mass 9xx10^-5 g is kept over a large horizontal sheet of charge having surface charge density 5x10^-5 C m^-2 What charge should be given to this particle so that if released, it does not fall down?

Two pith-balls each weighing 10^-3 kg are suspended from the same point by mans of silk threads 0.5 m long. On charging the pith-balls equally, they are found to repel each other to a distance of 0.2 m. Calculate the charge on each ball?

A wire AB is carrying a steady current of 12A and is lying on the table. Another wire CD carrying 5A is held directly above AB at a height of 1mm. Find the mass per unit length of the wire CD so that it remains suspended at its position when left free. Give the direction of the current flowing in CD with respect to that in AB. [Take the value of g = 10ms^-2 ]