21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 7, Problem 10QP
To determine
Select the correct option for the period of the spherical object when the radius is halved even the spin
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Students have asked these similar questions
If the rotational curve (orbital speed versus distance from center) of a spherically symmetric object is flat, what is implied about the mass density?
A. It remains constant at all distance from center.
B. It increases with distance from center.
C. It decreases with distance from center.
D. It remains zero far from the center because the distribution is essentially a point mass.
Is the answer B? Orbital velocity is still the same as the distance from the centre increases. By Mr = v2r/G, Mass increases with increasing radius when velocity is kept constant. So, galaxies with flat rotational curves indicate they contain large amounts of dark matter, especially further out from the centre. Thank you for clarifying my understanding!
1. What is the orbital angular mom ent um of the elect ron in the third orbit? (Ans. 3xh =
1.97 x 10-15eV).
Scenario
A meterstick is set on the edge of a table so that all
but a negligible bit of its length is off the edge of the
table as shown. The meterstick is released from rest
horizontally. The meterstick's mass is M and its
length is L. The rotational inertia of the meterstick
around the end is I =ML.
Ост
100cm
%3D
Chapter 7 Solutions
21st Century Astronomy
Ch. 7.1 - Prob. 7.1CYUCh. 7.2 - Prob. 7.2CYUCh. 7.3 - Prob. 7.3CYUCh. 7.4 - Prob. 7.4CYUCh. 7.5 - Prob. 7.5CYUCh. 7 - Prob. 1QPCh. 7 - Prob. 2QPCh. 7 - Prob. 3QPCh. 7 - Prob. 4QPCh. 7 - Prob. 5QP
Ch. 7 - Prob. 6QPCh. 7 - Prob. 7QPCh. 7 - Prob. 8QPCh. 7 - Prob. 9QPCh. 7 - Prob. 10QPCh. 7 - Prob. 11QPCh. 7 - Prob. 12QPCh. 7 - Prob. 13QPCh. 7 - Prob. 14QPCh. 7 - Prob. 15QPCh. 7 - Prob. 16QPCh. 7 - Prob. 17QPCh. 7 - Prob. 18QPCh. 7 - Prob. 19QPCh. 7 - Prob. 20QPCh. 7 - Prob. 21QPCh. 7 - Prob. 22QPCh. 7 - Prob. 23QPCh. 7 - Prob. 24QPCh. 7 - Prob. 25QPCh. 7 - Prob. 26QPCh. 7 - Prob. 27QPCh. 7 - Prob. 28QPCh. 7 - Prob. 29QPCh. 7 - Prob. 30QPCh. 7 - Prob. 31QPCh. 7 - Prob. 32QPCh. 7 - Prob. 33QPCh. 7 - Prob. 34QPCh. 7 - Prob. 35QPCh. 7 - Prob. 36QPCh. 7 - Prob. 37QPCh. 7 - Prob. 38QPCh. 7 - Prob. 39QPCh. 7 - Prob. 40QPCh. 7 - Prob. 41QPCh. 7 - Prob. 42QPCh. 7 - Prob. 43QPCh. 7 - Prob. 44QPCh. 7 - Prob. 45QP
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- Neutron 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_forward10.- Prove that the minimum angle that the angular momentum makes with the z-axis is Omín = sin-1arrow_forward2. In a binary star system, the two stars orbit the center of mass of the system. If both stars have the same mass M, the center of mass will be midway between the stars. Assume the orbital radius is R. Answer in terms of G, M and R. a. Determine the orbital speed of the stars. (Your answer should not be the same as the answer for 1b.) Note that the Earth and moon also actually both orbit around the center of mass of the Earth-moon system. However, the Earth is so much more massive than the moon that the center of mass is very close to the center of the Earth and as an approximation we say the moon orbits around the Earth. b. A space probe is exactly halfway between the two stars. Determine the minimum speed the space probe must be moving so that it can escape from the binary star-that is the space probe can just reach an infinite distance away from the stars. This speed is called the escape speed. C. * We want to just reach infinity. This means we will have zero speed at infinity.…arrow_forward
- Formation of a Neutron Star A star rotates with a period of 32 days about an axis through its center. The period is the time interval required for a point on the star's equator to make one complete revolution around the axis of rotation. After the star undergoes a supernova explosion, the stellar core, which had radius of 1.1 x 104 km, collapses into a neutron star of radius 3.6 km. Determine the period of rotation of the neutron star. SOLUTION Conceptualize The change in the neutron star's motion is similar to that of the skater described earlier in the textbook, but in the reverse direction. As the mass of the star moves closer to the rotation axis, we expect the star to spin faster Categorize Let us assume that during the collapse of the stellar core, (1) no external torque acts on it, (2) it remains spherical with the same relative mass distribution, and (3) its mass remains constant. We categorize system in terms of angular momentum. We do not know the mass distribution of the…arrow_forwardQ7) The atomic nucleus uranium-235 has a spin of 2 h Estimate its speed!arrow_forwardCalculate the angular momentum of the sun's spin angular momentum (assuming the sun is a uniform sphere) and the four major planets Jupiter, Saturn, Uranus and Neptune, and prove that the sun's spin angular momentum is less than 0.5% of the total angular momentum of the solar system.arrow_forward
- 1 ) James wants to use a dsill, He needs to Know if it Spins fast 1.2 x 10" 쁜 to 3.72 x104 enough, He sees that one is advertised for rad to 3.72 x 104 rad through an ang le of 2.7x10" rad. is the angular accelesa tion B) What is the time it takes flsas to go from 2.00 x104 rad to 8.53 x104 rad ?arrow_forward7. Determine the velocity of the electron in a positronium atom which is shown in the figure (figure is attached). Assume the radius of the positronium atom is 2 x 5.3 x 10^-9 cm a) What is the total angular momentum about the center of the positronium atom in Problem 7? b) What is the force on the electron due to the positron? (Give both magnitude and direction.) c) What is the electric potential energy of the positronium atom?arrow_forwardNeptune has a mass of 1.01026kg and is 4.5109km from the Sun with an orbital period of 165 years. Planetesimals in the outer primordial solar system 4.5 billion years ago coalesced into Neptune over hundreds of millions of years. If the primordial disk that evolved into our present day solar system had a radius of 1011km and if the matter that made up these planetesimals that later became Neptune was spread out evenly on the edges of it, what was the orbital period of the outer edges of the primordial disk?arrow_forward
- The Sun’s mass is 2.01030kg , its radius is 7.0105km , and it has a rotational period of approximately 28 days. If the Sun should collapse into a white dwarf of radius 3.5103km , what would its period be if no mass were ejected and a sphere of uniform density can model the Sun both before and after?arrow_forwardUsing the solution from the previous problem, find the increase in rotational kinetic energy, given the core’s mass is 1.3 times that of out Sun. Where does this increase in kinetic energy come from?arrow_forwardWhat happens to the orbital velocity of an object revolving around Earth if we reduce its height to one-fourth of the original one? A. The magnitude of the orbital velocity will be quadrupled. B. The magnitude of the orbital velocity will be doubled. C. The magnitude of the orbital velocity will be reduced by a factor of 4. D. The magnitude of the orbital velocity will be halved. Determine the GPE of a 300kg-object that is 2700km above Jupiter. Mass of Jupiter = 1.898 × 10^27 kg and radius of Jupiter is 69,911 km. A. 3.25 x 10^11 J B. 4.11 x 10^13 J C. 5.23 x 10^11 J D. 1.41 x 10^13 J The handwriting or solutions please make it clear (readable) please thank youarrow_forward
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