A horizontal straight wire 10m long extending from east to west is falling with a speed of 5m pert sec.at right angles to the horizontal componen of the earths magnetic field 0.3 X 10 n^ -4

I know the answer to emf induced

Please in detail xplain me how to use flemings right hand rule here Becoz only direction of force is known i.e downward .. which is at high potential and why !!M not clear !

The above Diagram is the top view.
Lets now see the front view of the wire. If you are facing the North then:

Now see carefully
we know that

F = q V X B
V= velocity od matal rod downward
B is magnetic field pointing toward you.
Now curl your fingers from V towards B so thumb gives you direction of Magnetic Force on protons to the left (West) where positive charge gets accumlated so it is at higher potential and the othe end at lower potential at electron move towards Right (East)