Question
Question: 41 forks are so arranged that each produces 5 beat/sec when sounded with its near fork. If the frequ...
41 forks are so arranged that each produces 5 beat/sec when sounded with its near fork. If the frequency of last fork is double the frequency of first fork, then the frequencies of the first and last fork respectively
A
200, 400
B
205, 410
C
195, 390
D
100, 200
Answer
200, 400
Explanation
Solution
Let the frequency of first tuning fork = n and that of last = 2n
n, n + 5, n + 10, n + 15 …… 2n this forms A.P.
Formula of A.P l = a + (N – 1) r where l = Last term, a = First term, N = Number of term, r = Common difference
2n = n + (41 – 1) 5
2n = n + 200
n = 200 and 2n = 400