A point particle of mass $M$ is attached to one end of a massless rigid non-conducting rod of length $L$. Another point particle of same mass is attached to the other end of the rod. The two particles carry charges $+q$ and $-q$ repectively. This arrangement is held in a region of uniform electric field $E$ such that the rod makes a small angle $(\theta <5^{\circ })$ with the field direction. The minimum time needed for the rod to become parallel to the field after it is set free. (rod rotates about centre of mass)

Q. A point particle of mass $M$ is attached to one end of a massless rigid non-conducting rod of length $L$. Another point particle of same mass is attached to the other end of the rod. The two particles carry charges $+q$ and $-q$ repectively. This arrangement is held in a region of uniform electric field $E$ such that the rod makes a small angle $(\theta <5^{\circ })$ with the field direction. The minimum time needed for the rod to become parallel to the field after it is set free. (rod rotates about centre of mass)

Q. A point particle of mass M attached to one end of a massless rigid non-conducting rod of length I. Another point particle of the same mass is attached to the other end of the rod. The two particles carry charges +q and -q respectively. This arrangement is held in a region of a uniform electric field E such that the rod makes a small angle $\theta$ (say of about 5 degrees) with the field direction. Find an expression for the minimum time needed for the rod to become parallel to the field after it is set free.

Q. Two point masses, m each carrying charges -q and +q are attached to the ends of a massless rigid non-conducting wire of length 'L'. When this arrangement is placed in a uniform electric field, then it deflects through an angle $\theta$. The minimum time needed by rod to align itself along the field is :

Q. A particle of mass $m$ and charge $q$ is attached to a light rod of length $L$. The rod can rotate freely in the plane of paper about the other end, which is hinged at $P$. The entire assembly lies in a uniform electric field $E$ also acting in the plane of paper as shown. The rod is released from rest when it makes an angle $\theta$ with the electric field direction. Determine the speed of the particle when the rod is parallel to the electric field.

Q. A particle of mass $m$ and charge $q$ is attached to a light rod of length $L$. The rod can rotate freely in the plane of paper about the other end, which is hinged at $P$. The entire assembly lies in a uniform electric field $E$ also acting in the plane of paper as shown. The rod is released from rest when it makes an angle $\theta$ with the electric field direction. (Assume gravity free speace)