# velocity question (1 Viewer)

#### akkjen

##### Active Member
i keep getting C, answer is B, thanks

#### akkjen

##### Active Member
also are people finding the sample questions hard or is it just me?

#### Drdusk

##### π
Moderator
Yeah I'm getting (B) as well? I measured r_Q as 6cm and r_P as 3cm approximately. It really doesn't matter that much.

Using the ratio we get

$\bg_white \dfrac{V_{qesc}}{V_{porb}} = \dfrac{\sqrt{\dfrac{2GM}{r_Q}}}{\sqrt{\dfrac{GM}{r_P}}}$

$\bg_white = \sqrt{\dfrac{2r_P}{r_Q}} = \sqrt{\dfrac{2\times 3cm}{6cm}}$

$\bg_white = 1$

#### akkjen

##### Active Member
Yeah I'm getting (B) as well? I measured r_Q as 6cm and r_P as 3cm approximately. It really doesn't matter that much.

Using the ratio we get

$\bg_white \dfrac{V_{qesc}}{V_porb} = \dfrac{\sqrt{\dfrac{2GM}{r_Q}}}{\sqrt{\dfrac{GM}{r_P}}}$

$\bg_white = \sqrt{\dfrac{2r_P}{r_Q}} = \sqrt{\dfrac{2\times 3cm}{6cm}}$

$\bg_white = 1$
yes B is correct, thanks