Giancoli 7th Edition textbook cover
Giancoli's Physics: Principles with Applications, 7th Edition
1
Introduction, Measurement, Estimating
Change chapter

1-4: Measurement, Uncertainty, Significant Figures
1-5 and 1-6: Units, Standards, SI, Converting Units
1-7: Order-of-Magnitude Estimating
1-8: Dimensions

Question by Giancoli, Douglas C., Physics: Principles with Applications, 7th Ed., ©2014, Reprinted by permission of Pearson Education Inc., New York.
Problem 27
Q

Estimate how many hours it would take to run (at 10 km/h) across the U.S. from New York to California.

A
500 hours, or 60 days
Giancoli 7th Edition, Chapter 1, Problem 27 solution video poster
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VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. Time is distance divided by speed so we have 5000 kilometers to go from New York to California divided by 10 kilometers an hour which we'll assume is the running speed here and so that's gonna work out to 500 hours and let's multiply that by 1 day for every 8 hours 8 hours of running you know, you have to sleep or at least take rest for the rest of the day and that means it would take about 60 days if you were to run about 8 hours per day to get across the US.

COMMENTS
By robina.winkler on Tue, 6/2/2020 - 2:39 PM

your answers do not match the answers in the back of the book. it seems they were looking for the 500h. answer alone.

By Mr. Dychko on Tue, 6/9/2020 - 5:51 PM

Yes, and the question does ask "how many hours..." I've added the number of hours to the quick answer.

By brandi_cantu1 on Sun, 9/5/2021 - 8:58 PM

Thank you!

By Mr. Dychko on Tue, 9/7/2021 - 7:11 PM

I'm glad it was helpful!

By GnosisFreu on Sat, 1/7/2023 - 5:24 AM

How were we supposed to know, or why does the textbook assume that we know the distance between new york and California? Where does the 5000 number come from? The question only provided 10 km per hour for speed

By anc89 on Thu, 12/21/2023 - 2:51 AM

I have the same question as GnosisFreu. Thank you!

By Mr. Dychko on Thu, 12/21/2023 - 6:36 PM

Hi anc89, thank you for your question. I think I looked up the approximate distance from New York to California. Keep in mind that this section of chapter 1 is about "Order-of-Magnitude Estimating" - your precision is meant to be low. The question says "California" which is itself not precise since it begs the question of where in California. This lack of precision is the point in this section since you're meant to get comfortable with making estimations that should be precise to only one significant figure, with some expected error in that figure, which is another way of saying an "order of magnitude" estimate.
Hope this helps,
Shaun

By anc89 on Thu, 12/21/2023 - 6:43 PM

Thank you, Mr.Dychko! I appreciate your subscription service and the time taken to help us understand physics better!

By Mr. Dychko on Thu, 12/21/2023 - 11:48 PM

Hi anc89, thank you so much for this wonderful feedback! Comments like this make the work worth while, and I'm really glad my solutions are helping so much with your studies.
With very best wishes,
Shaun

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