Answer:
A perfectly elastic collision conserves momentum and kinetic energy..
This property is called "Opacity".
The question is worded in a difficult way. A more easily understood wording of this question would be:
"<em>What is the name of the property of a material that prevents light passing through?"</em>
Answer:
4776.98 N is the minimum force to start the rise.
Explanation:
We can use the first Newton's law to find the minimum force to move the block.
So we will have:

Where:
- F is the force
- W(x) is the weight of the block in the x direction, W = mg*sin(15)
- F(f) is the static friction force (F(f) = μN), μ is the static friction coefficient 0.4.





Therefore 4776.98 N is the minimum force to move the block.
I hope it helps you!
The answer to the question would be Refraction.
as we know the two possible answers are refraction and reflection. The questions shows a decrease in speed thus being refraction as a ray in a reflection would not lose its speed. Hope this helps!