Explanation :
When a person is sliding with constant velocity, the forces that are acting on him are :
(1) Weight, W = mg where g is acceleration due to gravity.
(2) Friction forces acting opposite to the direction of motion.
(3) Normal force.
The forces acting on the person is balanced because the person is sliding with constant velocity.
From figure it is clear that, friction force is balanced by 
and normal is balanced by 
.
In the first figure, the surface absorbs all colors except for green light, which is reflected: so, the surface will appear as green to our eyes, because green is the only color which is reflected by that surface.
Similarly, in the second figure, the surface absorbs all colors except for blue, and so the surface will appear blue to our eyes.
In the third figure, the surface absorbs all colors, so it will appear black to our eyes (because no colors are reflected, and black=absence of colors).
In the fourth figure, all colors are reflected: this means the surface will appear white to our eyes (white= sum of all colors).
Answer:
They use noise control, creating a wave that negates outside or ambient sound and replaces it with the desired sound that listeners request.
Explanation:
I hope this helped
A window is the most transparent object from these, so that is the answer.
