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 very far apart their grav8(op*9gtr ss2 wy z3bvjo1 2u8c0pgpm itational potentibm5h5mf 4/v zwal energy is zero; when they are separated by ahmf zv/m54b5 w distance $d$ 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 potezpq5b:an(+it,. 7eky+ ydykrntial energy $U$ 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 $U' = -GMm/(2d) = \frac{1}{2} \left( -GMm/d \right) = U/2$.
| 
