本题目来源于试卷: 2007美国US F=MA物理竞赛，类别为 美国F=MA物理竞赛
[单选题]
When two stars are v ue,-)ksc3k9v/9xx srrl4qac ery far apart their gra+.*qs(d tfbosj36uif vitational potential energy is zero; when they are separated by a disto bt6qf dj si+(s*u3.fance $d$ the gravitational potential energy of the system is $U$. If the stars are separated by a distance $2d$ the gravitational potential energy of the system is
A. $U/4$
B. $U/2$
C. $U$
D. $2U$
E. $4U$
参考答案: B
本题详细解析:
The gravitational potential enlshm5g0vn tt.f j.fa 3q8grwt+v,gzr73 0 b4r ergy $U$ of two masses is given by $U(r) = -GMm/r$, where $r$ is the separation distance.
At distance $d$, we are given $U = -GMm/d$.
At distance $2d$, the new potential energy $U'$ is $U' = -GMm/(2d) = \frac{1}{2} \left( -GMm/d \right) = U/2$.
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