If this case could ever happen, the speed would follow from this formula:

with f the frequency and lambda the wavelength. We are give a wavelength of 10m. The frequencies of the visible light can range between 400 to about 790 Terahertz, so let us pick a middle point of 600 THz ("green-ish") as a "representative."

The speed of such a wave would have to be 6e+15 m/s (which would be 7 orders of magnitude higher than the universal speed of light constant)
When sitting down there is gravity , when sat down the chair is pushing back at a equal but opposite force
<h2>5.3 km</h2>
Explanation:
This question involves continuous displacement in various directions. When it becomes difficult to imagine, vector analysis becomes handy.
Let us denote each of the individual displacements by a vector. Consider the unit vectors
as the unit vectors in the direction of East and North respectively.
By simple calculations, we can derive the unit vectors
in the directions North,
South of West and
North of West respectively.
So Total displacement vector = Sum of individual displacement vectors.
Displacement vector = 
Magnitude of Displacement = 
∴ Total displacement = 
Answer:
Total length of spring 0.647 m
Explanation:
We have given mass of the person m = 150 kg
Acceleration due to gravity 
Spring constant k = 10000 N/m
Nominal length of spring = 0.50
According to hook's law


x = 0.147 m
So total length of spring = 0.50+0.147 = 0.647 m