(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Given: G = 6.67259 × 10^−11 Nm2/kg2

Two hypothetical planets of masses 2.5 × 10^23 kg and 7.8×10^23 kg and radii 3.2×10^6 m

and 7.1×10^6 m, respectively, are at rest when

they are an infinite distance apart. Because

of their gravitational attraction, they head

toward each other on a collision course.

When their center-to-center separation is

4.5 × 10^8 m, find their relative velocity. An-

swer in units of m/s.

2. Relevant equations

3. The attempt at a solution

F=GMm/r^2

M=7.8e23 kg

m=2.5e23 kg

Ki+Ui=Kf+Uf

r=4.5e8+3.2e6 +7.1e6=460300000m

0+0=.5mv^2+(-GMm/r)

.5v^2=GM/r

v=475.54 m/s

Is this answer correct?

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# Homework Help: Planetary collision problem

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