[tex] \text{Let acceleration=a}\\
a=g \sin \theta\\
sin \theta=\frac{3}{7}\\
\implies a=\frac{3g}{7}\\
\text{Now,}\\
v^2=u^2+2as\\
v^2= 0^2+2\times \frac{3g}{7}\times 7\\
v^2=6g\\
v=\sqrt{6g}=\sqrt{60}=7.8m/sec[/tex]
