Pebbles usually become smooth and rounded by being polished by water, sand polished by winds, or by tumbling and exposing other sides to erosive effects.
D. the last choice because the info above tells u so
Explanation:
Given
initial speed(u)=3 m/s
mass of each ball is m
Let the cue ball is moving in x direction initially
In elastic collision Energy and momentum is conserved
Let u be the initial velocity and
be the final velocity of 8 ball and cue ball respectively

The angle after which cue ball is deflected is given by

Conserving momentum in x direction


Along Y axis


substitute the value of 
we get 

Answer:
0.029%
Explanation:
Weight on the surface is given by,

The acceleration due to gravity at given height is,

The weight in another height is equal to





The change of the Weight is,

Answer:
n = 1.4266
Explanation:
Given that:
refractive index of crystalline slab n = 1.665
let refractive index of fluid is n.
angle of incidence θ₁ = 37.0°
Critical angle 

According to Snell's law of refraction:

At point P ; 

Therefore:

Then maximum value of refractive index n of the fluid is:


n = 1.4266