Question from http://www.sgforums.com/forums/2297/topics/270298
A star has radius 10km and mass 2.5 * 109 kg. A meteor is drawn into its gravitational field. Calculate the speed with which it will strike the surface of the star. Neglect initial speed of meteor.
*************************
Answer:
Here, we must use the GPE formula P = -GMm/r
where:
G = 6.673 * 10-11
M = mass of star
m = mass of meteor
r = radius = 10 000m
The change in GPE = gain in KE of the meteor
Hence
change in GPE = 0 - (-GMm/r)
gain in KE = 1/2 m v² - 0
Hence, GMm/r = 1/2 m v²
Put all the values in
we get v² = 3.3365 * 1015
Thus, v = 5.8*107 m/s
