Ch 01: Units, Physical Quantities & Vectors

Young & Freedman Calc - University Physics 15th Edition

Young & Freedman Calc15th EditionUniversity PhysicsISBN: 9780135159552Not the one you use?Change textbook

Young & Freedman Calc 15th Edition

Ch 01: Units, Physical Quantities & Vectors

Problem 20

Chapter 1, Problem 20

How many times does a human heart beat during a person's lifetime? How many gallons of blood does it pump?

Verified step by step guidance

Estimate the average number of heartbeats per minute. A typical resting heart rate is about 70 beats per minute.

Calculate the number of heartbeats per year. Multiply the average heartbeats per minute by the number of minutes in an hour, hours in a day, and days in a year. Use the formula:

70 \times 60 \times 24 \times 365

Estimate the average lifespan in years. For example, you might use 80 years as a typical lifespan.

Calculate the total number of heartbeats over a lifetime by multiplying the number of heartbeats per year by the average lifespan. Use the formula:

70 \times 60 \times 24 \times 365 \times 80

Estimate the total gallons of blood pumped. Assume the heart pumps about 1.5 gallons of blood per minute. Multiply the gallons per minute by the number of minutes in a lifetime using the formula:

1.5 \times 60 \times 24 \times 365 \times 80

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Average Heart Rate

The average heart rate is the number of times the heart beats per minute. For adults, this typically ranges from 60 to 100 beats per minute. Understanding this rate is crucial for estimating the total number of heartbeats over a lifetime, as it provides a baseline for calculations.

Lifetime Duration

Lifetime duration refers to the average lifespan of a human, which is essential for calculating the total number of heartbeats and blood pumped. The average human lifespan is approximately 70-80 years, and using this figure allows for a comprehensive estimation of heart activity over a person's life.

Cardiac Output

Cardiac output is the volume of blood the heart pumps per minute, typically around 5 to 6 liters in adults. This concept is vital for determining the total gallons of blood pumped over a lifetime, as it combines heart rate and stroke volume to quantify blood circulation.

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For the vectors A and B in Fig. E1.24, use a scale drawing to find the magnitude and direction of the vector sum A + B

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