In the milky way, the most abundant gas in emission nebulae is

Hydrogen

Explanation: The emission nebula are clouds made up of ionised gases that emits their own light at a particular wavelength. They generally range from 100 to 10,000 solar masses.

The most common type of the emission nebula occurs when the interstellar gas clouds are dominated by the hydrogen gas.

They emit UV photons that breaks the hydrogen atoms into hydrogen nuclei and electrons.

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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