is used in many home smoke alarms. If 10% of the americium in a smoke detector decays in 180 years, what is the half-life of this isotope

the answer to your question is c.

if you read the house of usher you should know that the house was haunted

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.

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