Why does a cloud collapse rapidly at first, and then slow down as the it gets denser?
What will be an ideal response?
The self-gravity causes the cloud to collapse. Gravitational potential energy is turned to heat (through friction) and released as infrared light from the cloud. As the cloud continues to collapse and becomes smaller and denser, molecules collide more frequently and do not have time to release their excess energy as photons. The thermal energy in the cloud is trapped and its temperature rises. The rising temperature increases the pressure and slows down the collapse.
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An elliptical galaxy could
a. evolve into an irregular galaxy when it has used up all of its gas and dust. b. be formed from the collision and merger of spiral galaxies. c. evolve from a single spiral galaxy when the spiral has used up all of its gas and dust. d. become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster. e. evolve from an S0 galaxy if the S0 galaxy were to increase its rotation rate.
Super-Earths are:
A) planets that are most earthlike, likely to harbor life. B) planets that are a few times the mass of the Earth. C) planets that have earthlike masses, but orbit much closer to their star than the Earth does to the Sun. D) any rocky (or terrestrial) planet. E) Earth-mass planets that are much lower in density than the Earth, giving them larger radii.
The x component of the velocity of an object vibrating along the x-axis obeys the equation vx(t) = (0.445 m/s) sin[(25.4 rad/s)t + 0.223]
(a) What is the amplitude of the motion of this object? (b) What is the maximum acceleration of the vibrating object?
When an acrobat hangs motionless from a pair of rings
a. she has no measurable weight. b. her weight depends on the angles the ropes make with the ceiling. c. her weight is reduced by the upward force the rings exert on her. d. her weight is increased by the upward force the rings exert on her. e. she exerts a gravitational force on the Earth that is equal to the sum of the forces the rings exert on her.