Which one among the following is used to make periscope?

Potential at a point due to a point charge is V. The charge is doubled and also the distance of the point from the charge is doubled. The new potential is

A neutral (uncharged) metal ball is suspended using a non-magnetic string. A positively charged insulating rod is placed near the ball which is observed to be attracted to the rod. This is because

Which one among the following is the correct value of the gravitational force of the Earth acting on a body of mass 1 kg?

A body is thrown upward against the gravity ‘g’ with initial velocity ‘u’. Which one among the following is the correct expression for its final velocity when the body attains the maximum height?

 If the ratio of the weight of a man in a stationary lift and when it is moving downwards with uniform acceleration ‘a’ is 3 : 2, then the value of ‘a’ is