# [SOLVED]Derivative of the flight path angle

#### dwsmith

##### Well-known member
Why is this true?
$$h = rv_{\perp} = r(r\dot{\nu})\Rightarrow\dot{\nu} = \frac{h}{r^2}$$
Look at the last page here to see a visualization.

#### chisigma

##### Well-known member
Why is this true?
$$h = rv_{\perp} = r(r\dot{\nu})\Rightarrow\dot{\nu} = \frac{h}{r^2}$$
Look at the last page here to see a visualization.
If $\displaystyle v_{\perp}$ is the radial speed is $\displaystyle v_{\perp}= r\ \dot{\nu}$ where $\nu$ is the angle in radians...

Kind regards

$\chi$ $\sigma$

#### dwsmith

##### Well-known member
If $\displaystyle v_{\perp}$ is the radial speed is $\displaystyle v_{\perp}= r\ \dot{\nu}$ where $\nu$ is the angle in radians...

Kind regards

$\chi$ $\sigma$
Wouldn't $v_{\perp}$ be the tangential speed? $v_r$ I would think is the radial speed.