Answer:
Part a)

Part b)
t = 12 s
Explanation:
Part a)
Tension in the rope at a distance x from the lower end is given as

so the speed of the wave at that position is given as

here we know that

now we have


Part b)
time taken by the wave to reach the top is given as




Answer:
Explanation:
Pressure due to fluid is directly proportional to the depth of fluid, density of the fluid and the value of acceleration due to gravity.
P = h d g
Where, h is the depth, d be the density and g be the acceleration due to gravity.
If we talk about teh atmospheric pressure, the density of air goes on decreasing as we go up and up. o we cannot say that it is directly depends only on the depth of air, it also depends on the changing density of air.
The mass of the box would be 30!