Answer:
Time = t = 6.62 s
Explanation:
Given data:
Height = h = 215 m
Initial velocity =
= 0 m/s
gravitational acceleration = g = 9.8 m/s²
Time = t = ?
According to second equation of motion

As initial velocity is zero, So the first term of right hand side of above equation equal to zero.

t² = 
t =
t = 
t = 6.62 s
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Answer:
Approximately
.
Explanation:
The refractive index of the air
is approximately
.
Let
denote the refractive index of the glass block, and let
denote the angle of refraction in the glass. Let
denote the angle at which the light enters the glass block from the air.
By Snell's Law:
.
Rearrange the Snell's Law equation to obtain:
.
Hence:
.
In other words, the angle of refraction in the glass would be approximately
.
K.E. = 1/2 mv²
K.E. is directly proportional to v^2
So, when K.E. increase by 2, K.E. increase by root. 2
v' = 1.41v
original v value was 3 so, final would be:
v' = 1.41*3 = 4.23
After round-off to it's tenth value, it will be:
v' = 4.2
So, option B is your answer!
Hope this helps!