Answer:

Explanation:
The ratio of pressure 2 to 1 us 5.48/1= 5.48 rounded off as 5.5.
Referring to table A.2 of modern compressible flow then 
Also
and making
the subject of the formula then
Making reference to
diagram then

32.5 kg of air
Explanation:
To calculate the mass of the air, we use the density formula:
density = mass / volume
mass = density × volume
density of air = 1.3 kg/m³
volume = 5 × 3 × 2 = 25 m³
mass of the air = 1.3 kg/m³ × 25 m³
mass of the air = 32.5 kg
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Answer:
7.50 cm
Explanation:
The formula
1/v + 1/u = 1/f
Is used.
where.
u is the object distance.
v is the image distance.
f is the focal length of the lens.
1/v + 1/15 = 1/5
1/v = 1/5 - 1/15
1/v = (3-1)/15
1/v = 2/15
2v = 15
V = 15/2
V = 7.5 cm
For focal length, f in lens is always taken as negative for concave and positive for convex. ... And for image distance, V in lens it is taken as positive in Convex lens since image is formed on +X side. It is taken as negative in Concave lens since image is formed in -X side of the Cartesian.