Answer:

Explanation:
When she moved a distance of 1 m from mid point she observe first destructive interference due to two speakers
so we can say that path difference of sound due to two speakers will be equal to half of the wavelength
so path difference is given as

so it will be


now we know that


now frequency of sound is given as



Answer:
Time period of the osculation will be 0.0671 sec
Explanation:
It is given a vertical spring is stretched by 4 cm
So change in length of the spring x = 4 cm = 0.04 m
Mass which is hung from it m = 12 gram = 0.012 kg
Sprig force will be equal to weight of the mass
So 

k = 244.7 N/m
Now new mass is m = 28 gram = 0.028 kg
So time period with new mass will be


The formula for both is v(t) = v0 + a*t
b) v(8) = 0 + 6m/s^2 *8s = 48 m/s
now we know the beginning (2) and end speed (14), but not the time:
c) 14 = 2 + 1.5*t => t = (14-2)/1.5 = 8 seconds
Answer:
23.52092 J
Explanation:
m = Mass of block = 6.79 kg
s = Sliding distance = 2.82 m
= Angle of slide = 20.7°
= Coefficient of kinetic friction = 0.425
g = Acceleration due to gravity = 9.8 m/s²
Work done by the force of gravity is given by

The work done by the force of gravity is 23.52092 J