box A conducting rod is held horizontally in an east–west direction.
The magnetic flux density of the Earth’s magnetic field is 4.9 × 10−5 T and is directed
at an angle of 68° to the ground.
0 3 . 1 Figure 5 shows the arrangement. The rod has a length of 2.0 m.
Figure 5
The rod is released and falls 8.0 m to the ground. It remains in a horizontal
east–west direction as it falls.
Determine the average emf across the rod during its fall to the ground.
Assume that air resistance is negligible.
[3 marks]
So the diagram shows the rod falling vertically down and the magnetic field is at an angle of 68 degrees. So with the values given i know it has to be e=blvcos(68). however I do not understand why we use the final velocity before it hits the ground as v in the emf equation. Because in the question it states average emf, but if we use the max value of velocity would that not give us the max emf.
Note : the correct answer is 4.5x10^-4v, which is obtained by using the max/final velocity v which is 12.5