Physics
The ringing of an electric bell in an enclosed evacuated glass bell jar is not heard outside because

There is no air or any other gas in the bell jar
The ringing is not loud enough
The glass of the bell jar absorbs the sound waves
The bell jar is too small

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Physics
The Hooke's law is valid for

Only proportional region of the stress strain curve
Entire stress strain curve
Entire elastic region of the stress strain curve
Elastic as well as plastic region of the stress strain curve

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