Which vehicle will have more kinetic energy, a parked semitruck or a car moving at 50 km/h?
1 answer:
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It will take 267 milliseconds for a sample of radon-218 to decay from 99 grams to 0. 50 grams.
We know that half life of a first order reaction is given by:
where k = rate of reaction
Given half life = 35 milliseconds
So from this we get k = 0.0198
Now we know that rate of first order reaction is given by:
where t= time
R'= initial amount = 99 g
R= final amount= 0.50 g
k= rate of reaction = 0.0198
Putting values of these in above equation we get t=267 milliseconds.
i.e. It will take 267 milliseconds for a sample of radon-218 to decay from 99 grams to 0. 50 grams.
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(a) Zero
The maximum efficiency (Carnot efficiency) of a heat engine is given by
where
is the low-temperature reservoir
is the high-temperature reservoir
For the heat engine in the problem, we have:
Therefore, the maximum efficiency is
(b) Zero
The efficiency of a heat engine can also be rewritten as
where
W is the work performed by the engine
is the heat absorbed from the high-temperature reservoir
In this problem, we know
Therefore, since the term cannot be equal to infinity, the numerator of the fraction must be zero as well, which means
W = 0
So the engine cannot perform any work.