Answer:
The right answer for this question is 85%.
(I had the same question.)
Answer:
The value is 
Explanation:
From the question we are told that
The current is 
The inductor is 
The voltage induced is 
Generally the emf induced is mathematically represented as

Here
is the time taken
=> 
=> 
=> 
Answer:
Average speed = 46.67 m/s
Explanation:
Given that the time taken in covering first 1000 m = 25 seconds.
The time taken in covering next 2.5 km = 50 seconds.
Total distance covered = 1000 m + 2500 m = 3500 m
Total time taken = 25+50=75 seconds
Average speed = Total distance covered / total time taken
= 3500/75 = 46.67 m/s
The correct choice is
D. 22 Hz and 42 Hz.
In fact, the beat frequency is given by the difference between the frequencies of the two waves:

In this problem, the beat frequency is
, therefore the only pair of frequencies that gives a difference equal to 20 Hz is
D. 22 Hz and 42 Hz.