Doubt from electrodynamics

q1). A long wire having linear charge density lambda moving with constant velocity  along its length. A
point charge moving with same speed in opposite direction and at that instant it is r distance from the
wire. The net force acting on the charge is given by

q2)Electrons are projected into the region of an electric field E between the plates P1 and P2 with
velocity u making an angle theta with the horizontal plate P1 at O, as shown in the figure. The minimum
electric force which allows the electrons to leave the field region along the direction parallel to the
plates P1 and P2 (i.e., along x - axis in the figure) is [Electron charge is e and mass is m]

q3)A non conducting spherical shell of radius R having charge distributions +q and –q is released from
rest on a horizontal non conducting rough surface as shown in figure in a horizontal electric fied E.
The initial value of friction force so that sphere does not slip is

q4)A particle of mass m and positive charge q is projected towards an infinitely long line of a charge
(having linear density of charge lambda ) from a distance 0
r . The direction of initial velocity v makes
an angle theta
30 with the normal to the line of charge as shown in figure. The minimum distance of
approach of the charge particle with the line of charge will be (neglect gravity)

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