Physics for Scientists and Engineers: Foundations and Connections
1st Edition
ISBN: 9781133939146
Author: Katz, Debora M.
Publisher: Cengage Learning
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Question
Chapter 12, Problem 14PQ
(a)
To determine
The period of the pulsar’s rotation.
(b)
To determine
The number of seconds by which the period increases each second.
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Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. The density of a neutron star is roughly 1014 times as great as that of ordinary solid matter. Suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. The star’s initial radius was 7.0 * 105 km (comparable to our sun); its final radius is 16 km. If the original star rotated once in 30 days, find the angular speed of the neutron star.
A star with mass m, period Ti = 30 days, and radius ri = 1E4 km collapses into a neutron star with a radius of rf = 3 km. Our goal will be to determine the period Tf of the neutron star. Useful formulae: Li=Lf; L=lw; w=2πf=2π/T; Isphere=2/5mr2
How much angular momentum Li does the star have before it collapses?
Group of answer choices:
A)riTi
B)mr2i
C)mivi
D)Iiwi
What is the rotation rate wi of the star before collapsing?
Group of answer choices
A)riTi
B)mr2i
C)2π/Ti
D)2πfi
Suppose we model the star as a solid sphere of radius ri with moment of inertia 2/5mr2i (a good assumption). What does our description of Li read now?
Group of answer choices
A)2/5mr2i(2πfi)
B)2/5mr2i(2π/Ti)
C)2/5mr2i(mr2i)
D)2/5mr2i(riTi)
How much angular momentum Lf does the star have after it collapses?
Group of answer choices
A)mfvf
B)rfTf
C)I fwf
D)mr2f
What is the rotation rate wf of the star after collapsing?
Group of answer choices
A)2π/Tf…
Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. The density of a neutron star is roughly 1014 times as great as that of ordinary solid matter. Suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. The star’s initial radius was 7.0 * 105 km, its final radius is 16 km. If the original star rotated once in 30 days, find the angular speed of the neutron star.
Chapter 12 Solutions
Physics for Scientists and Engineers: Foundations and Connections
Ch. 12.1 - Figure 12.5 shows two rotating objects. Indicate...Ch. 12.2 - Prob. 12.2CECh. 12.2 - Prob. 12.3CECh. 12.2 - Prob. 12.4CECh. 12.2 - Prob. 12.5CECh. 12.5 - For each exercise shown in Figure 12.22, how does...Ch. 12 - Often, we model the Moon as a particle in a...Ch. 12 - Suppose a satellite orbits the Earth such that it...Ch. 12 - Prob. 3PQCh. 12 - Prob. 4PQ
Ch. 12 - A ceiling fan is rotating counterclockwise with a...Ch. 12 - As seen from above the Earths North Pole, the...Ch. 12 - A rotating objects angular position is given by...Ch. 12 - A rotating objects angular position is given by...Ch. 12 - Jupiter rotates about its axis once every 9 hours...Ch. 12 - Prob. 10PQCh. 12 - Prob. 11PQCh. 12 - Prob. 12PQCh. 12 - Prob. 13PQCh. 12 - Prob. 14PQCh. 12 - Prob. 15PQCh. 12 - A disk rolls up an inclined plane as shown in...Ch. 12 - Jeff, running outside to play, pushes on a...Ch. 12 - A potters wheel rotating at 240 rev/min is...Ch. 12 - Friction in an old clock causes it to lose 1...Ch. 12 - A wheel starts from rest and in 12.65 s is...Ch. 12 - Prob. 21PQCh. 12 - Starting from rest, a wheel reaches an angular...Ch. 12 - A potters wheel is rotating with an angular...Ch. 12 - The angular speed of a wheel is given by (t) =...Ch. 12 - Prob. 25PQCh. 12 - Prob. 26PQCh. 12 - An electric food processor comes with many...Ch. 12 - Prob. 28PQCh. 12 - A bicyclist is testing a new racing bike on a...Ch. 12 - Prob. 30PQCh. 12 - A disk is initially at rest. A penny is placed on...Ch. 12 - Prob. 32PQCh. 12 - Consider again the two wind turbines in Problem...Ch. 12 - Consider again the two wind turbines in Problem...Ch. 12 - In testing an automobile tire for proper...Ch. 12 - Prob. 36PQCh. 12 - A merry-go-round at a childrens park begins at...Ch. 12 - A wheel rotating at a constant rate of 1850...Ch. 12 - Why are doorknobs placed on the edge opposite the...Ch. 12 - Prob. 40PQCh. 12 - Prob. 41PQCh. 12 - Prob. 42PQCh. 12 - A wheel of inner radius r1 = 15.0 cm and outer...Ch. 12 - A uniform plank 6.0 m long rests on two supports,...Ch. 12 - Prob. 45PQCh. 12 - Prob. 46PQCh. 12 - Prob. 47PQCh. 12 - Prob. 48PQCh. 12 - Prob. 49PQCh. 12 - Prob. 50PQCh. 12 - Prob. 51PQCh. 12 - Given a vector A=4.5+4.5j and a vector B=4.5+4.5j,...Ch. 12 - A square plate with sides 2.0 m in length can...Ch. 12 - Prob. 54PQCh. 12 - A disk with a radius of 4.5 m has a 100-N force...Ch. 12 - Disc jockeys (DJs) use a turntable in applying...Ch. 12 - Prob. 57PQCh. 12 - Prob. 58PQCh. 12 - A wheel initially rotating at 85.0 rev/min...Ch. 12 - Prob. 60PQCh. 12 - A centrifuge used for training astronauts rotating...Ch. 12 - Problems 62 and 63 are paired. 62. C A disk is...Ch. 12 - Prob. 63PQCh. 12 - A potters wheel rotates with an angular...Ch. 12 - Prob. 65PQCh. 12 - Prob. 66PQCh. 12 - Prob. 67PQCh. 12 - Lara is running just outside the circumference of...Ch. 12 - The propeller of an aircraft accelerates from rest...Ch. 12 - A ball rolls to the left along a horizontal...Ch. 12 - Three forces are exerted on the disk shown in...Ch. 12 - Consider the disk in Problem 71. The disks outer...Ch. 12 - Prob. 73PQCh. 12 - Prob. 74PQCh. 12 - Prob. 75PQCh. 12 - Prob. 76PQCh. 12 - Prob. 77PQCh. 12 - Prob. 78PQCh. 12 - Prob. 79PQCh. 12 - Prob. 80PQCh. 12 - If the rod in Problem 79 is in equilibrium, what...Ch. 12 - As a compact disc (CD) spins clockwise as seen...Ch. 12 - A disk-shaped machine part has a diameter of 40.0...Ch. 12 - Prob. 84PQ
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- Two planets X and Y travel counterclockwise in circular orbits about a star as shown in Figure P11.14. The radii of their orbits are in the ratio 3:1. At one moment, they are aligned as shown in Figure P11.14a, making a straight line with the star. During the next five years, the angular displacement of planet X is 90.0 as shown in Figure P11.14b. What is the angular displacement of planet Y at this moment?arrow_forwardNeutron stars are extremely dense objects formed from the remnants of supernova explosions. Many rotate very rapidly. Suppose the mass of a certain spherical neutron star is twice the mass of the Sun and its radius is 10.0 km. Determine the greatest possible angular speed it can have so that the matter at the surface of the star on its equator is just held in orbit by the gravitational force.arrow_forwardNeutron stars are extremely dense objects that are formed from the remnants of supernova explosions. Many rotate very rapidly. Suppose the mass of a certain spherical neutron star is twice the mass of the Sun and its radius is 10.0 km. Determine the greatest possible angular speed the neutron star can have so that the matter at its surface on the equator is just held in orbit by the gravitational force.arrow_forward
- Two stars M1 and M2 of equal mass make up a binary star system. They move in a circular orbit that has its center at the midpoint of the line that separates them. If M1 = M2 = 8.20 sm (solar mass), and the orbital period of each star is 2.70 days, find their orbital speed. (The mass of the sun is 1.99 10^30 kg.) km/s.arrow_forwardA star with mass m, period Ti = 30 days, and radius ri = 1E4 km collapses into a neutron star with a radius of rf = 3 km. Our goal will be to determine the period Tf of the neutron star. Useful formulae: Li=Lf; L=lw; w=2πf=2π/?; Isphere=2/5mr2 How much angular momentum Li does the star have before it collapses? Group of answer choices: A)riTi B)mr2i C)mivi D)Iiwi What is the rotation rate ??ωi of the star before collapsing? Group of answer choices A)riTi B)mr2i C)2π/Ti D)2πfi Suppose we model the star as a solid sphere of radius ri with moment of inertia 2/5mr2i (a good assumption). What does our description of Li read now? Group of answer choices A)2/5??2i(2πfi) B)2/5??2i(2π/Ti) C)2/5??2i(mr2i) D)2/5??2i(riTi) How much angular momentum Lf does the star have after it collapses? Group of answer choices A)mfvf B)rfTf C)I fwf D)mr2f What is the rotation rate wf of the star after collapsing? Group of answer choices A)2π/Tf…arrow_forwardA star with a mass of 3.41 x 1030 kilograms and a radius of 8.20 x 108 meters rotates on its axis once every 33 days. a. What is the angular momentum of the star? Include units in your answer. b. After running out of fusible matter, the star collapses under its own gravity to form a pulsar with a radius of 24.1 kilometers. What is the period of rotation of the pulsar? Include units in your answer.arrow_forward
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