CP Dark Nebulae and the Interstellar Medium. The dark area in Fig. P18.83 that appears devoid of stars is a dark nebula, a cold gas cloud in interstellar space that contains enough material to block out light from the stars behind it. A typical dark nebula is about 20 light-years in diameter and contains about 50 hydrogen atoms per cubic centimeter (monatomic hydrogen, not H 2 ) at about 20 K. (A light-year is the distance light travels in vacuum in one year and is equal to 9.46 × 10 15 m.) (a) Estimate the mean free path for a hydrogen atom in a dark nebula. The radius of a hydrogen atom is 5.0 × 10 −11 m. (b) Estimate the rms speed of a hydrogen atom and the mean free time (the average time between collisions for a given atom). Based on this result, you think that atomic collisions, such as those leading to H 2 molecule formation, are very important in determining the composition of the nebula? (c) Estimate the pressure inside a dark nebula. (d) Compare the rms speed of a hydrogen atom to the escape speed at the surface of the nebula (assumed spherical). If the space around the nebula were a vacuum, would such a cloud be stable or would it tend to evaporate? (e) The stability of dark nebulae is explained by the presence of the interstellar medium (ISM), an even thinner gas that permeates space and in which the dark nebulae are embedded. Show that for dark nebulae to be in equilibrium with the ISM, the numbers of atoms per volume ( N/V ) and the temperatures ( T ) of dark nebulae and the ĨSM must be related by ( N / V ) nebula ( N / V ) ISM = T ISM T nebula (f) In the vicinity of the sun, the ISM contains about 1 hydrogen atom per 200 cm 3 . Estimate the temperature of the ISM in the vicinity of the sun. Compare to the temperature of the sun’s surface, about 5800 K. Would a spacecraft coasting through interstellar space burn up? Why or why not? Figure P18.83
CP Dark Nebulae and the Interstellar Medium. The dark area in Fig. P18.83 that appears devoid of stars is a dark nebula, a cold gas cloud in interstellar space that contains enough material to block out light from the stars behind it. A typical dark nebula is about 20 light-years in diameter and contains about 50 hydrogen atoms per cubic centimeter (monatomic hydrogen, not H 2 ) at about 20 K. (A light-year is the distance light travels in vacuum in one year and is equal to 9.46 × 10 15 m.) (a) Estimate the mean free path for a hydrogen atom in a dark nebula. The radius of a hydrogen atom is 5.0 × 10 −11 m. (b) Estimate the rms speed of a hydrogen atom and the mean free time (the average time between collisions for a given atom). Based on this result, you think that atomic collisions, such as those leading to H 2 molecule formation, are very important in determining the composition of the nebula? (c) Estimate the pressure inside a dark nebula. (d) Compare the rms speed of a hydrogen atom to the escape speed at the surface of the nebula (assumed spherical). If the space around the nebula were a vacuum, would such a cloud be stable or would it tend to evaporate? (e) The stability of dark nebulae is explained by the presence of the interstellar medium (ISM), an even thinner gas that permeates space and in which the dark nebulae are embedded. Show that for dark nebulae to be in equilibrium with the ISM, the numbers of atoms per volume ( N/V ) and the temperatures ( T ) of dark nebulae and the ĨSM must be related by ( N / V ) nebula ( N / V ) ISM = T ISM T nebula (f) In the vicinity of the sun, the ISM contains about 1 hydrogen atom per 200 cm 3 . Estimate the temperature of the ISM in the vicinity of the sun. Compare to the temperature of the sun’s surface, about 5800 K. Would a spacecraft coasting through interstellar space burn up? Why or why not? Figure P18.83
CP Dark Nebulae and the Interstellar Medium. The dark area in Fig. P18.83 that appears devoid of stars is a dark nebula, a cold gas cloud in interstellar space that contains enough material to block out light from the stars behind it. A typical dark nebula is about 20 light-years in diameter and contains about 50 hydrogen atoms per cubic centimeter (monatomic hydrogen, not H2) at about 20 K. (A light-year is the distance light travels in vacuum in one year and is equal to 9.46 × 1015 m.) (a) Estimate the mean free path for a hydrogen atom in a dark nebula. The radius of a hydrogen atom is 5.0 × 10−11 m. (b) Estimate the rms speed of a hydrogen atom and the mean free time (the average time between collisions for a given atom). Based on this result, you think that atomic collisions, such as those leading to H2 molecule formation, are very important in determining the composition of the nebula? (c) Estimate the pressure inside a dark nebula. (d) Compare the rms speed of a hydrogen atom to the escape speed at the surface of the nebula (assumed spherical). If the space around the nebula were a vacuum, would such a cloud be stable or would it tend to evaporate? (e) The stability of dark nebulae is explained by the presence of the interstellar medium (ISM), an even thinner gas that permeates space and in which the dark nebulae are embedded. Show that for dark nebulae to be in equilibrium with the ISM, the numbers of atoms per volume (N/V) and the temperatures (T) of dark nebulae and the ĨSM must be related by
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(f) In the vicinity of the sun, the ISM contains about 1 hydrogen atom per 200 cm3. Estimate the temperature of the ISM in the vicinity of the sun. Compare to the temperature of the sun’s surface, about 5800 K. Would a spacecraft coasting through interstellar space burn up? Why or why not?
air is pushed steadily though a forced air pipe at a steady speed of 4.0 m/s. the pipe measures 56 cm by 22 cm. how fast will air move though a narrower portion of the pipe that is also rectangular and measures 32 cm by 22 cm
No chatgpt pls will upvote
13.87 ... Interplanetary Navigation. The most efficient way
to send a spacecraft from the earth to another planet is by using a
Hohmann transfer orbit (Fig. P13.87). If the orbits of the departure
and destination planets are circular, the Hohmann transfer orbit is an
elliptical orbit whose perihelion and aphelion are tangent to the
orbits of the two planets. The rockets are fired briefly at the depar-
ture planet to put the spacecraft into the transfer orbit; the spacecraft
then coasts until it reaches the destination planet. The rockets are
then fired again to put the spacecraft into the same orbit about the
sun as the destination planet. (a) For a flight from earth to Mars, in
what direction must the rockets be fired at the earth and at Mars: in
the direction of motion, or opposite the direction of motion? What
about for a flight from Mars to the earth? (b) How long does a one-
way trip from the the earth to Mars take, between the firings of the
rockets? (c) To reach Mars from the…
Chapter 18 Solutions
University Physics with Modern Physics (14th Edition)
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