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Chapter 1: 22 (page 28)
How many times does a human heart beat during a person鈥檚 lifetime? How many gallons of blood does it pump? (Estimate that the heart pumps 50 cm3 of blood with each beat.)
The human heart beats 3027456000 time in whole lifetime.
The heart pump 400 million gallon of blood in whole life time.
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A small rock is thrown vertically upward with a speed of22.0 m/s from the edge of the roof of a 30.0-m-tall building. Therock doesn鈥檛 hit the building on its way back down and lands onthe street below. Ignore air resistance. (a) What is the speed of therock just before it hits the street? (b) How much time elapses fromwhen the rock is thrown until it hits the street?
For a spherical planet with mass , volume , and radius ,derive an expression for the acceleration due to gravity at the planet鈥檚 surface, , in terms of the average density of the planet, , and the planet鈥檚 diameter, . The table gives the values of and for the eight major planets:
(a) Treat the planets as spheres. Your equation for as a function of
and
shows that if the average density of the planets is constant, a graph of
versus
will be well represented by a straight line. Graph
as a function of
for the eight major planets. What does the graph tell you about the variation in average density? (b) Calculate the average density for each major planet. List the planets in order of decreasing density, and give the calculated average density of each. (c) The earth is not a uniform sphere and has greater density near its center. It is reasonable to assume this might be true for the other planets. Discuss the effect this nonuniformity has on your analysis. (d) If Saturn had the same average density as the earth, what would be the value of
at Saturn鈥檚 surface?
You are on the roof of the physics building, above the ground (Fig. P2.70). Your physics professor, who istall, is walking alongside the building at a constant speed of. If you wish to drop an egg on your professor鈥檚 head, where should the professor be when you release the egg? Assume that the egg is in free fall.
(Fig. P2.70)
In describing the size of a large ship, one uses such expressions as 鈥渋t displaces 20,000 tons.鈥� What does this mean? Can the weight of the ship be obtained from this information?
Express each approximation of 蟺 to six significant figures: (a) 22/7 and (b) 355/113. (c) Are these approximations accurate to that precision?
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