<u>Answer:</u> The correct answer is Option b.
<u>Explanation:</u>
Young's Modulus is defined as the ratio of stress acting on a substance to the amount of strain produced.
Stress is defined as force per unit area and strain is defined as proportional deformation in a material.
The equation representing Young's Modulus is:

where,
Y = Young's Modulus
F = force exerted by the weight
l = length of wire
A = area of cross section
= change in length
Hence, the correct answer is Option b.
90+66=156
156/2=78
Reply:78kilometers in 2 hours.
Here stress is parallel to the surface of the body. So it's a Shear stress.
<u>Answer :</u>
(a) d = 0.25 m
(b) d = 0.5 m
<u>Explanation :</u>
It is given that,
Frequency of sound waves, f = 686 Hz
Speed of sound wave at
is, v = 343 m/s
(1) Perfectly destructive interference occurs when the path difference is half integral multiple of wavelength i.e.
........(1)
Velocity of sound wave is given by :




Hence, when the speakers are in phase the smallest distance between the speakers for which the interference of the sound waves is perfectly destructive is 0.25 m.
(2) For constructive interference, the path difference is integral multiple of wavelengths i.e.
( n = integers )
Let n = 1
So, 


Hence, the smallest distance between the speakers for which the interference of the sound waves is maximum constructive is 0.5 m.
Answer:

Explanation:
Average speed is given by
where
is total distance and
is time.
Plugging in given values, we get:
.