Answer:
527 Hz
Solution:
As per the question:
Beat frequency of the player, 
Frequency of the tuning fork, f = 523 Hz
Now,
The initial frequency can be calculated as:


when

when

But we know that as the length of the flute increases the frequency decreases
Hence, the initial frequency must be 527 Hz
Answer:
(a) 
(b) 
(c) 
Explanation:
(a) According to Newton's second law, the acceleration of a body is directly proportional to the force exerted on it and inversely proportional to it's mass.

(b) According to Newton's third law, the force that the sled exerts on the girl is equal in magnitude but opposite in the direction of the force that the girl exerts on the sled:

(c) Using the kinematics equation:

For the girl, we have
and
. So:

For the sled, we have
. So:

When they meet, the final positions are the same. So, equaling (1) and (2) and solving for t:

Now, we solve (1) for 

The land was frozen everywhere and a part of the ocean froze over to create a bridge between two countries. Some people may disagree with me over the ice bridge, though.
Answer:
1/4 λ film
Explanation:
Let L = total path length then L = 2 t where t is film thickness
There will be a 180 deg phase change at the air-film interface but no
phase change at the film-air interface
L = n * wavelength / 2 where n = 1, 3, 5, 7 etc
(the total path L must be an odd number of 1/2 wavelengths)
Or t = n * wavelength / 4 (the film must be an odd number
of 1/4 wavelengths thick)
1/4 λ film satisfies this condition
Note: Find the missing diagram in the attachment section.