The figure shows an elastic collision of two pucks (masses \( m_{A}=0.500 \) kg and \( m_{B}=0.300 \mathrm{~kg} \) ) on a frictionless air-hockey table. Puck \( A \) has an initial velocity of \( 4.00 \mathrm{~m} / \mathrm{s} \) in the positive \( x \)-direction and a final velocity of \( 2.00 \mathrm{~m} / \mathrm{s} \) in an unknown direction \( \alpha \). Puck B is initially at rest. Find the final speed \( v_{B 2} \) of puck \( B \) and the angles \( \alpha \) and \( \beta \).
You solved
\[
\begin{array}{l}
m_{A}=0.5 \mathrm{~kg} \\
u_{A}=4 \mathrm{im} / \mathrm{s} \\
v_{A}=2 \mathrm{~m} / \mathrm{s} .
\end{array}
\]
By conseruation of lainebie erergy.
a)
\[
\begin{array}{l}
v_{2} m_{A} u_{A}^{2}+x_{2} m_{B} u_{B}^{2}=y_{2} m_{A} v_{A}^{2}+v_{2} m_{B} v_{B}^{2} \\
\therefore v_{B}^{2}=\frac{m_{A} u_{A}^{2}-m_{A} v_{A}^{2}}{m_{B}} \quad\left(=u_{B=0}\right) \\
\therefore v_{B}=\sqrt{\frac{(0.5)(4)^{2}-(0.5)(2)^{2}}{0.3}}=4.47 \mathrm{~m} / \mathrm{s}
\end{array}
\]
(b) By conseruation if momentum lueget.
Frx-Direction \( m_{A} u_{A x}=m_{A} v_{A x}+m_{B} v_{B x} \)
\[
(0.5)(4)=(0.5)(2)+\cos \alpha)+(0.3)(4.47) \cos \beta
\]
In \( y \)-Direction
\[
\begin{array}{l}
\text { rection } \quad 0=m_{A} v_{A y}+m_{B} V_{B y} \quad\left(\because u_{A y}=u_{B y}=0\right) \\
0=(0.5)(2) \sin \alpha+(0.3)(-4.47 \sin \beta)
\end{array}
\]
By solving (1) and (2) lueget.
\[
\alpha=36.9^{\circ}, \quad \beta=26.6^{\circ}
\]