Astronomy
Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Chapter 2, Problem 14E

Why did Pythagoras believe that Earth should be spherical?

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5.77 A block with mass m₁ is placed on an inclined plane with slope angle a and is connected to a hanging block with mass m₂ by a cord passing over a small, frictionless pulley (Fig. P5.74). The coef- ficient of static friction is μs, and the coefficient of kinetic friction is Mk. (a) Find the value of m₂ for which the block of mass m₁ moves up the plane at constant speed once it is set in motion. (b) Find the value of m2 for which the block of mass m₁ moves down the plane at constant speed once it is set in motion. (c) For what range of values of m₂ will the blocks remain at rest if they are released from rest?
5.78 .. DATA BIO The Flying Leap of a Flea. High-speed motion pictures (3500 frames/second) of a jumping 210 μg flea yielded the data to plot the flea's acceleration as a function of time, as shown in Fig. P5.78. (See "The Flying Leap of the Flea," by M. Rothschild et al., Scientific American, November 1973.) This flea was about 2 mm long and jumped at a nearly vertical takeoff angle. Using the graph, (a) find the initial net external force on the flea. How does it compare to the flea's weight? (b) Find the maximum net external force on this jump- ing flea. When does this maximum force occur? (c) Use the graph to find the flea's maximum speed. Figure P5.78 150 a/g 100 50 1.0 1.5 0.5 Time (ms)
5.4 ⚫ BIO Injuries to the Spinal Column. In the treatment of spine injuries, it is often necessary to provide tension along the spi- nal column to stretch the backbone. One device for doing this is the Stryker frame (Fig. E5.4a, next page). A weight W is attached to the patient (sometimes around a neck collar, Fig. E5.4b), and fric- tion between the person's body and the bed prevents sliding. (a) If the coefficient of static friction between a 78.5 kg patient's body and the bed is 0.75, what is the maximum traction force along the spi- nal column that W can provide without causing the patient to slide? (b) Under the conditions of maximum traction, what is the tension in each cable attached to the neck collar? Figure E5.4 (a) (b) W 65° 65°

Chapter 2 Solutions

Astronomy

Ch. 2 - The Sun was once thought to be a planet. Explain...Ch. 2 - Is the ecliptic the same thing as the celestial...Ch. 2 - What is an asterism? Can you name an example?Ch. 2 - Why did Pythagoras believe that Earth should be...Ch. 2 - How did Aristotle deduce that the Sun is farther...Ch. 2 - What are two ways in which Aristotle deduced that...Ch. 2 - How did Hipparchus discover the wobble of Earth’s...Ch. 2 - Why did Ptolemy have to introduce multiple circles...Ch. 2 - Why did Copernicus want to develop a completely...Ch. 2 - What two factors made it difficult, at first, for...Ch. 2 - What phases would Venus show if the geocentric...Ch. 2 - Describe a practical way to determine in which...Ch. 2 - What is a constellation as astronomers define it...Ch. 2 - Draw a picture that explains why Venus goes...Ch. 2 - Show with a simple diagram how the lower parts of...Ch. 2 - Parallaxes of stars were not observed by ancient...Ch. 2 - Why do you think so many people still believe in...Ch. 2 - Consider three cosmological perspectives-the...Ch. 2 - The north celestial pole appears at an altitude...Ch. 2 - What were two arguments or lines of evidence in...Ch. 2 - Although the Copernican system was largely correct...Ch. 2 - During a retrograde loop of Mars, would you expect...Ch. 2 - The Great Pyramid of Giza was constructed nearly...Ch. 2 - Explain why more stars are circumpolar for...Ch. 2 - What is the altitude of the north celestial pole...Ch. 2 - If you were to drive to some city south of your...Ch. 2 - Hipparchus could have warned us that the dates...Ch. 2 - Explain three lines of evidence that argue against...Ch. 2 - What did Galileo discover about the planet Jupiter...Ch. 2 - What did Galileo discover about Venus that cast...Ch. 2 - Suppose Eratosthenes had found that, in...Ch. 2 - Suppose Eratosthenes’ results for Earth’s...Ch. 2 - Suppose you are on a strange planet and observe,...
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