C because of the positioning of the initial ray of refraction
Answer: Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.
Explanation:
4. 1 and 2 only.
1. the downward force is the force of gravity.
<span>2. The upward force exerted is the Normal reaction from the floor.</span>
Answer:

Explanation:
The angular momentum of an object is given by:

where
m is the mass of the object
v is its velocity
r is the distance of the object from axis of rotation
Here we have:
m = 350 g = 0.35 kg is the mass of the ball
v = 9.0 m/s is the velocity
r = 3.0 m is the distance of the object from axis of rotation (if we take the ground as the centre of rotation)
Therefore, the angular momentum is:

Here we have to calculate the number of rotations made by earth around its own axis in the entire life time of a human being.
The average human life is 50 years .
Each year is 365.5 days
Hence 
=18,275 days
The earth rotates around its own axis in 23 hours 56 minutes and 4 second which is approximately equal to 24 hours or one days.
Hence one rotation takes one days.
⇒18,275 days =18,275 rotations
Hence the total number of rotations made by earth around its own axis in the life time of a average human life time will be 18,275 times