# physics launch angle

• Sep 16th 2009, 04:21 PM
BiGpO6790
physics launch angle
[IMG]file:///C:/Users/Nick/AppData/Local/Temp/moz-screenshot-4.jpg[/IMG][IMG]file:///C:/Users/Nick/AppData/Local/Temp/moz-screenshot-5.jpg[/IMG]cant figure this out

A ball is to be shot from level ground toward a wall at distance x (Figure 4-46a). Figure 4-46b shows the y component vy of the ball's velocity just as it would reach the wall, as a function of that distance x. What is the launch angle?
• Sep 16th 2009, 05:13 PM
skeeter
Quote:

Originally Posted by BiGpO6790
[IMG]file:///C:/Users/Nick/AppData/Local/Temp/moz-screenshot-4.jpg[/IMG][IMG]file:///C:/Users/Nick/AppData/Local/Temp/moz-screenshot-5.jpg[/IMG]cant figure this out

image ?

A ball is to be shot from level ground toward a wall at distance x (Figure 4-46a). Figure 4-46b shows the y component vy of the ball's velocity just as it would reach the wall, as a function of that distance x. What is the launch angle?

use $\displaystyle g = 10 \, m/s^2$

from the graph ...

$\displaystyle v_y = 5 - \frac{x}{2}$

$\displaystyle v_y = v_y(0) + a_y \cdot t = 5 - 10t$

$\displaystyle x = 20t$

$\displaystyle v_x = 20 \, m/s$

since $\displaystyle v_y(0) = 5 \, m/s$

$\displaystyle \theta = \arctan\left(\frac{5}{20}\right)$