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Calculate the average density in kilograms [kg] per cubic meter [m3] for a White Dwarf with a mass of

1 solar mass and the size of planet Earth. Be sure to use the correct units. (b) Calculate your own weight on the surface of the white dwarf star.

User NemoXP
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1 Answer

4 votes

Answer:

(a) 2 × 10^9 kg/m^3; (b) roughly the mass of the Statue of Liberty.

Explanation:

(a) Density of white dwarf:

D = m/V

Data:

1 solar mass = 2 × 10^30 kg

1 Earth radius = 6.371 × 10^6 m

Calculations:

V = (4/3)πr^3 = (4/3)π × (6.371 × 10^6 m)^3 = 1.083 × 10^21 m^3

D = 2 × 10^30 kg/1.083 × 10^21 m^3 = 2 × 10^9 kg/m^3

2. Weight on a white dwarf

The formula for weight is

w = kMm/r^2

where

k = a proportionality constant

M = mass of planet

m = your mass

w(on dwarf)/w(on Earth) = [kM(dwarf)m/r^2] /[kM(Earth)m/r^2

k, m, and r are the same on both planets, so

w(on dwarf)/w(on Earth) = M(dwarf)/M(Earth)

w(on dwarf) = w(on Earth) × [M(dwarf)/M(Earth)]

Data:

M(Earth) = 6.0 × 10^24 kg

Calculation:

w(on dwarf) = w(on Earth) × (2 × 10^30 kg /6.0 × 10^24 kg)

= 3.3 × 10^5 × w(on Earth)

Thus, if your weight on Earth is 60 kg, your weight on the white dwarf will be

3.3 × 10^5 × 60 kg = 2 × 10^7 kg

That's roughly as heavy as the Statue of Liberty is on Earth.

User Syed Waleed
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