Question

1- What is the mass of air in a room measuring 10m x 5m x 2m, If the density of air is is 1.3 kg m -³

2-The speed of an electric locomotive is 90km/hr. Express this Speed in m/s.
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Answer 1

Part 1:

Given:

• Density = 1.3 kg/m³
• Volume = 10 m × 5 m × 2 m = 100 m³

To find:

Mass = ?

Solution:

Mass = Density × Volume

⇒ Mass = 1.3 × 100

⇒ Mass = 130 kg

∴ Mass of air = 130 kg

Part 2:

Given:

Speed in km/hr = 90 km/hr

To find:

Speed in m/sec = ?

Solution:

To convert speed in km/hr to m/sec, multiply the given number by 5/18

★ According to the question,

Speed in m/sec = 5/18 × 90

⇒ Speed in m/sec = (90 × 5) ÷ 18

⇒ Speed in m/sec = 25 m/sec

∴ Speed in m/s = 25 m/s