In a gas at (absolute) temperature t, the molecules have a typical kinetic energy of 3kbt/2, where kb is boltzmann’s constant.
derive an expression for the thermal debroglie wavelength, a typical value for the debroglie wavelength λ of a molecule in the gas.
for helium atoms, calculate the debroglie wavelength at room temperature and at the boiling point of helium, and compare each number with the typical distance between the particles in each state.
comment on when we will need to use quantum mechanics in understanding the behavior of helium.

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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b.

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answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.