Dust reddens starlight because it a. emits mostly in the infrared due to its cold temperature. b. re-emits the light it absorbs at red wavelengths. c. preferentially affects light at visible and shorter wavelengths. d. is made mostly of hydrogen, which produces the red h-alpha emission line. e. primarily moves away from earth.

c. preferentially affects light at visible and shorter wavelengths.

Dust conversely affects light at optical and shorter wavelength scattering it. It scatters high-frequency light. A few percent of interstellar dust particles is responsible for markedly dimming and reddening the starlight.

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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