Answer:
frequency of the sound = f = 1,030.3 Hz
phase difference = Φ = 229.09°
Explanation:
Step 1: Given data:
Xini = 0.540m
Xfin = 0.870m
v = 340m/s
Step 2: frequency of the sound (f)
f = v / λ
λ = Xfin - Xini = 0.870 - 0.540 = 0.33
f = 340 / 0.33
f = 1,030.3 Hz
Step 3: phase difference
phase difference = Φ
Φ = (2π/λ)*(Xini - λ) = (2π/0.33)* (0.540-0.33) = 19.04*0.21 = 3.9984
Φ = 3.9984 rad * (360°/2π rad)
Φ = 229.09°
Hope this helps!
The crate moves at constant velocity, this means that its acceleration is zero, so the net force acting on the crate is zero (Newton's second law).
There are only two forces acting on the crate: the force F applied by the worker and the frictional force, acting in the opposite direction:

, where

is the coefficient of friction and

is the mass of the crate. Since the net force should be equal to zero, the two forces must have same magnitude, so we have:

And so, this is the force that the worker must apply to the crate.
B. Greenhouse technology
Since the green house will help keep the pest and harmful conditions. The greenhouse will be able to control temperatures and will keep out harmful bugs. You/I will be able to provide the tree with the perfect sequence of growth.

When something is heated or cooled, its length changes by an amount proportional to the original length and the change in temperature: linear expansion : ΔL=αL0ΔT (α is the coefficient of linear expansion) The coefficient of linear expansion depends only on the material an object is made from.
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