# oldhw2_s - oldhomewk 02 YOO HEE Due 4:00 am 1 Question 1...

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Unformatted text preview: oldhomewk 02 YOO, HEE Due: Jan 17 2008, 4:00 am 1 Question 1, chap 1, sect 99. part 1 of 1 10 points Assume the Sun is mostly composed of hy- drogen atoms. Assume the mass of the Sun is 1 . 6 10 30 kg, and the mass of a hydrogen atom is 1 . 672 10- 27 kg. How many atoms are there in the Sun? Correct answer: 9 . 56938 10 56 atoms (toler- ance 1 %). Explanation: Basic Concepts: Elementary Arithmetic N atoms = M sun M atom = 1 . 6 10 30 kg 1 . 672 10- 27 kg = 9 . 56938 10 56 atoms . Question 2, chap 1, sect 99. part 1 of 1 10 points Assuming 83 . 9 heartbeats / min, estimate the total number of times the heart of a hu- man beats in an average lifetime of 97 years. Correct answer: 4 . 28049 10 9 heartbeats (tolerance 5 %). Explanation: The heart rate must be multiplied by the lifetime, with proper conversions heartbeats min min year years heartbeats A conversion factor for min year can be easily derived (60 min / h) (24 h / day) (365 . 256 day / year) = 525969 min / year lifetime heartbeats = (83 . 9 heartbeats / min) (525969 min / year) (97 years) = 4 . 28049 10 9 heartbeats . Question 3, chap 1, sect 99. part 1 of 1 10 points Assume: The diameter of the tire is 2 . 5 ft . An automobile tire is rated to last for 40000 mi. Estimate the number of revolutions the tire will make in its lifetime. Correct answer: 2 . 68908 10 7 rev (tolerance 1 %). Explanation: The diameter of a tire is 2 . 5 ft, with a circumference of C = d . Thus the tire would make (40000 mi) 5280 ft 1 mi 1 rev (2 . 5 ft) = 2 . 68908 10 7 rev . Question 4, chap 1, sect 6. part 1 of 1 10 points A fisherman catches two sturgeons. The smaller of the two has a measured length of 94.27 cm (two decimal places and four signif- icant figures), and the larger fish has a mea- sured length of 148.8 cm (one decimal placesured length of 148....
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## This note was uploaded on 05/04/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.

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oldhw2_s - oldhomewk 02 YOO HEE Due 4:00 am 1 Question 1...

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