Air spaces are used in insulation because air is a poor conductor.
This is an example of inertia - the body keeps it's energy because there is no force applied to it. When we try to stop it's motion, it resists. A man is not rigidly attached to the bus, so he keeps moving forward, at least until he hits the front window from inside. Answer is D.
Answer:
B. A system cannot take in additional matter.
Explanation: The total amount of energy in the universe remains constant, it can merely change from one form to another.
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Answer:0.318 revolutions
Explanation:
Given
Initially Propeller is at rest i.e. 
after 

using 


Revolutions turned in 2 s



To get revolution 
=