When light moves from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle above which there is no refracted ray, and it is given by:

(2)
where

is the refractive index of the second medium and

is the refractive index of the first medium.
We can find the ratio

by using Snell's law:

(1)
where

is the angle of incidence

is the angle of refraction
By using the data of the problem and re-arranging (1), we find

and if we use eq.(2) we can now find the value of the critical angle:
Answer:
1) El diámetro es de aproximadamente 913,987 cm.
2) La fuerza del cilindro es 5576850 kgf
Explanation:
1) Los parámetros dados son;
El volumen del aire = 13,122 litros = 13122000 cm³
La presión de trabajo = 8.5 kgf / cm²
La longitud del cilindro = 20 cm.
Por lo tanto, tenemos;
El área de la base del cilindro = π · r² = 13122000 cm³ / (20 cm) = 656100 cm²
r = √ (656100 / π) ≈ 456,994 cm
El diámetro = 2 × r ≈ 2 × 456.994 ≈ 913.987 cm
El diámetro ≈ 913,987 cm
2) La fuerza del cilindro = El área de la base del cilindro × La presión de trabajo
∴ La fuerza del cilindro = 656100 cm² × 8.5 kgf / cm² = 5576850 kgf
La fuerza del cilindro = 5576850 kgf
Answer:
The minimum stopping distance when the car is moving at
29.0 m/sec = 285.94 m
Explanation:
We know by equation of motion that,

Where, v= final velocity m/sec
u=initial velocity m/sec
a=Acceleration m/
s= Distance traveled before stop m
Case 1
u= 13 m/sec, v=0, s= 57.46 m, a=?

a = -1.47 m/
(a is negative since final velocity is less then initial velocity)
Case 2
u=29 m/sec, v=0, s= ?, a=-1.47 m/
(since same friction force is applied)

s = 285.94 m
Hence the minimum stopping distance when the car is moving at
29.0 m/sec = 285.94 m