Physics for Scientists and Engineers: Foundations and Connections
15th Edition
ISBN: 9781305289963
Author: Debora M. Katz
Publisher: Cengage Custom Learning
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Chapter 8, Problem 60PQ
Much of the mass of our Milky Way galaxy is concentrated in a central sphere of radius r = 2 kpc, where “pc” is the abbreviation for the unit “parsec”; 1 pc = 3.26 ly. Assume the Sun is in a circular orbit of radius r = 8.0 kpc around the central sphere of the Milky Way. The Sun’s orbital speed is approximately 220 km/s; assume the central sphere is at rest.
a. Estimate the mass in the inner Milky Way. Report your answer in kilograms and in solar masses.
b. What is the escape speed of the Milky Way?
c. CHECK and THINK: Do you believe that stars in the Milky Way have been observed to have speeds of 500 km/s? Explain.
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Our solar system is roughly 2.2 x 1020 m away from the center of the Milky Way galaxy, and the system is moving at roughly 231.4 km/s around the galaxy's center. Since most of the galaxy's mass is near its center (and we are on an outer arm of this spiral galaxy), let's model the galaxy has a spherical mass distribution (like a single, giant star that our system is orbiting around).
What is the mass of the galaxy (according to our rough, spherical model)? Obviously, this will be a VERY big answer, and so enter in your answer to the order of 1040 kg. In other words, calculate the answer, and then divide by 1040 and then enter in the result.
BTW - by assuming that all mass in the galaxy is made up of stars that are about the same mass as our sun, it isn't too hard to then estimate how many stars are in the galaxy!). As an another aside, some measurements and observations that we have taken in Astronomy suggests that in reality, stars only make up a fraction of the total mass
A star is 1.0 x 104 ly (light-years) from the center of its galaxy and is moving in a circle around that center at a speed of 110 km/s. (a) How long does it take the star to make one revolution about the galactic center? (b) How many revolutions has the star completed since it was formed about 5.6 x 109 years ago?
Astronomical observations of our Milky Way galaxy indicate that it has a mass of about 8.0 • 1011 solar masses. A star orbiting on the galaxy’s periphery is about 6.0 • 104 light years from its center.
a) What should the orbital period of that star be in years?
b) If its period is 6.0 • 107 years instead, what is the mass of the galaxy in solar masses? Such calculations are used to imply the existence of “dark matter” in the universe and have indicated, for example, the existence of very massive black holes at the centers of some galaxies.
Chapter 8 Solutions
Physics for Scientists and Engineers: Foundations and Connections
Ch. 8.1 - Comet Halleys Orbital Parameters Figure 8.1 shows...Ch. 8.2 - Prob. 8.2CECh. 8.2 - Prob. 8.3CECh. 8.3 - In Figure 8.11, a person launches a ball off of a...Ch. 8 - Case Study From Figure 8.1B for Comet Halley, is...Ch. 8 - Estimate the kinetic energy of the following: a....Ch. 8 - Prob. 3PQCh. 8 - Prob. 4PQCh. 8 - A 0.430-kg soccer ball is kicked at an initial...Ch. 8 - Prob. 6PQ
Ch. 8 - According to a scaled woman, a 67.7-kg man runs...Ch. 8 - Prob. 8PQCh. 8 - Prob. 9PQCh. 8 - Prob. 10PQCh. 8 - Prob. 11PQCh. 8 - Prob. 12PQCh. 8 - Prob. 13PQCh. 8 - In each situation shown in Figure P8.12, a ball...Ch. 8 - Prob. 15PQCh. 8 - Prob. 16PQCh. 8 - Prob. 17PQCh. 8 - Prob. 18PQCh. 8 - A ball of mass 0.40 kg hangs straight down on a...Ch. 8 - Prob. 20PQCh. 8 - Prob. 21PQCh. 8 - Prob. 22PQCh. 8 - One type of toy car contains a spring that is...Ch. 8 - A block is placed on top of a vertical spring, and...Ch. 8 - Rubber tends to be nonlinear as an elastic...Ch. 8 - A block is hung from a vertical spring. The spring...Ch. 8 - A spring of spring constant k lies along an...Ch. 8 - A block on a frictionless, horizontal surface is...Ch. 8 - A falcon is soaring over a prairie, flying at a...Ch. 8 - A stellar black hole may form when a massive star...Ch. 8 - A newly established colony on the Moon launches a...Ch. 8 - The Flybar high-tech pogo stick is advertised as...Ch. 8 - An uncrewed mission to the nearest star, Proxima...Ch. 8 - A small ball is tied to a string and hung as shown...Ch. 8 - Prob. 35PQCh. 8 - Prob. 36PQCh. 8 - Prob. 37PQCh. 8 - Prob. 38PQCh. 8 - Figure P8.39 shows two bar charts. In each, the...Ch. 8 - Prob. 40PQCh. 8 - If a spacecraft is launched from the Moon at the...Ch. 8 - A 1.50-kg box rests atop a massless vertical...Ch. 8 - A man unloads a 5.0-kg box from a moving van by...Ch. 8 - Starting at rest, Tina slides down a frictionless...Ch. 8 - Prob. 45PQCh. 8 - Karen and Randy are playing with a toy car and...Ch. 8 - An intrepid physics student decides to try bungee...Ch. 8 - A block of mass m = 1.50 kg attached to a...Ch. 8 - Prob. 49PQCh. 8 - A jack-in-the-box is actually a system that...Ch. 8 - A side view of a half-pipe at a skateboard park is...Ch. 8 - Prob. 52PQCh. 8 - Prob. 53PQCh. 8 - Prob. 54PQCh. 8 - A particle moves in one dimension under the action...Ch. 8 - Prob. 56PQCh. 8 - Prob. 57PQCh. 8 - Prob. 58PQCh. 8 - Prob. 59PQCh. 8 - Much of the mass of our Milky Way galaxy is...Ch. 8 - A stellar black hole may form when a massive star...Ch. 8 - Prob. 62PQCh. 8 - Prob. 63PQCh. 8 - FIGURE 8.38 Comparison of a circular and an...Ch. 8 - A 50.0-g toy car is released from rest on a...Ch. 8 - Prob. 66PQCh. 8 - The Earths perihelion distance (closest approach...Ch. 8 - After ripping the padding off a chair you are...Ch. 8 - A In a classic laboratory experiment, a cart of...Ch. 8 - A block is attached to a spring, and the block...Ch. 8 - At the start of a basketball game, a referee...Ch. 8 - At the start of a basketball game, a referee...Ch. 8 - Prob. 73PQCh. 8 - Prob. 74PQCh. 8 - At 220 m, the bungee jump at the Verzasca Dam in...Ch. 8 - Prob. 76PQCh. 8 - A block of mass m1 = 4.00 kg initially at rest on...Ch. 8 - A Eric is twirling a ball of mass m = 0.150 kg...Ch. 8 - Prob. 79PQCh. 8 - Prob. 80PQCh. 8 - Prob. 81PQCh. 8 - Prob. 82PQCh. 8 - Prob. 83PQCh. 8 - Prob. 84PQ
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