A person measures his or her heart rate by counting the number of beats in 30 s. If 40±1 beats are counted in 30±0.5 s, what is the heart rate and its uncertainty in beats per minute?
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SOLUTION:
In order to compute for the heart rate in beats per minute, we need to solve for the base. The base is
A=30sec40beats×1min60sec=80beats/min
Then we compute for the percent uncertainty by combining the uncertainties of the number of beats and time. That is
(a) Suppose that a person has an average heart rate of 72.0 beats/min. How many beats does he or she have in 2.0 y? (b) In 2.00 y? (c) In 2.000 y?
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SOLUTION:
Part a
This is a problem on rounding off. Take note that 72.0 has three significant figures, 2.0 has two significant figures, 2.00 has three significant figures, and 2.000 has four significant figures.
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