Two neutron stars are separated by a distance of 10^13 m. They each have a mass of 10^30 kg and a radius of 10^5 m. They are initially at rest with respect to each other.(adsbygoogle = window.adsbygoogle || []).push({});

(a) How fast are they moving when their separation has decreased to one-half its initial value?

My answer is 3.652 x 10^3 m/s , and it is wrong again (sigh).

here is my computations

1/2(mass)(final velocity)^2 - G(M1)(m2)/Final distance = 1/2(mass)(initial velocity)^2 - G(M1)(m2)/(initial radius)

Since they are initially at rest, the vi term is zero, and that kinetic energy term vanishes. Then i plug in the values and solve for final velocity:

1/2(10^30)(final velocity)^2 - (6.67x10^-11)(10^30)^2/(5x10^12) = -(6.67x10^-11)(10^30)^2/(10^13)

so I isolate for final velocity and i get (final velocity)^2 = 1.33 x 10^7

and i get final velocity = 3.652 x 10^3, when i input it it says it is wrong. Can someone help me, where did i go wrong? I did it multiple times already.

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# Homework Help: Physics problem, why is my answer wrong? HELPPP

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