Question

A planet moves around the sun. At a given point P, it is closed from the sun at a distance $v _ { 1 }$. At another point Q. when it is farthest from the sun at a distance $d _ { 2 }$, its speed will be

• A. $\frac { d _ { 1 } ^ { 2 } v _ { 1 } } { d _ { 2 } ^ { 2 } }$
• B. $\frac { d _ { 2 } v _ { 1 } } { d _ { 1 } }$
• C. $\frac { d _ { 1 } v _ { 1 } } { d _ { 2 } }$
• D. $\frac { d _ { 2 } ^ { 2 } v _ { 1 } } { d _ { 1 } ^ { 2 } }$

Answer 1

Answer: (C)

$\frac { d _ { 1 } v _ { 1 } } { d _ { 2 } }$

Answer 2

According to law of conservation of angular momentum $m v _ { 1 } d _ { 1 } = m v _ { 2 } d _ { 2 }$

$\therefore$ $v _ { 2 } = \frac { d _ { 1 } v _ { 1 } } { d _ { 2 } }$ .