21st Century Astronomy (sixth Edition)
6th Edition
ISBN: 9780393675504
Author: Laura Kay, Stacy Palen, George Blumenthal
Publisher: W. W. Norton & Company
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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).
2. 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.…
Chapter 7 Solutions
21st Century Astronomy (sixth Edition)
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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- Q7) 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_forward1 ) 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_forward
- 7. 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_forwardThe 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_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
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