To set up a stable and clear interference pattern, two conditions must be met: The sources of the waves must be coherent, which means they emit identical waves with a constant phase difference.
And what finish the question
Answer:
The required work done is 
Explanation:
Consider 'F' is the applied force on the crate and 'f' be the force created by friction. According to the figure if '
' be the coefficient of friction, then

where 'M', 'N' and 'g' are the mass of the crate, the normal force aced upon the block and the acceleration due to gravity respectively.
Since the application of force by the movers does not create any acceleration to the block, we can write

So the work done (W) in moving the crate by a distance s = 10.6 m is

Answer:
6 m/s²
Explanation:
From the question given above, the following data were obtained:
Velocity (v) = 30 m/s
Time (t) = 5 s
Acceleration (a) =..?
Acceleration is defined mathematically as:
Acceleration (a) = Velocity (v) /time (t)
a = v /t
With the above formula, we can obtain the acceleration of the object as follow:
Velocity (v) = 30 m/s
Time (t) = 5 s
Acceleration (a) =..?
a= v/t
a= 30/5
a = 6 m/s²
Therefore, the acceleration of the object is 6 m/s² due East.