Speed of a mass falling into a star given the mass and radius of the star

Thread starter TobiasZed
Start date Nov 21, 2023
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Mass Radius Speed

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SUMMARY

The discussion centers on calculating the speed of a mass falling into a star using the gravitational constant and the star's mass and radius. The formula applied was the square root of ((2)(6.67*10^-11)(3.90E+30))/(5.70E+7), which resulted in an incorrect value of 1.55*10^-5. Participants emphasized the importance of using correct units in calculations to achieve accurate results.

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Understanding of gravitational physics
Familiarity with the gravitational constant (6.67 x 10^-11 m^3 kg^-1 s^-2)
Knowledge of mass and radius measurements in astrophysics
Basic algebra for manipulating equations

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Nov 21, 2023

TobiasZed

Homework Statement: Beginning at rest at an extremely large separation, a ball is released and allowed to fall toward a star of mass 3.90E+30 kg and radius 5.70E+7 m. What is the speed of the ball when it reaches the surface?

Relevant Equations: square root of (2*G*M)/(r)

I tried the square root of ((2)(6.67*10^-11)(3.90E+30))/(5.70E+7)
I got 1.55*10^-5 and that is wrong. Maybe I am using the wrong equation but this is the one of professor gave me and I don't know what I am doing wrong :-(

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Nov 21, 2023

Hill

Check your calculation.

Nov 21, 2023

Orodruin

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… and use units!

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