Answer
$v = 6.4m/s$
Work Step by Step
$E_A = E_B$
$K_A + U_A= K_B + U_B$
$K_A = K_A + U_B - U_B$
$\frac{1}{2}mv^2_{_A} = \frac{1}{2}mv^2_{_B} +mgh_B -mgh_A $
$\frac{1}{2}mv^2_{_A} = \frac{1}{2}mv^2_{_B} +mg(h_B -h_A) $
$v^2_{_A} =2 \times \frac{ \frac{1}{2}mv^2_{_B} +mg(h_B -h_A)}{m} $
$v^2_{_A} = v^2_{_B} +2g(h_B -h_A)$
$v^2_{_A} = [8^2 +2\times 9.8(20 -(20\times cos20^{\circ}))]$
$v^2_{_A} = 40.5$
$v = \sqrt {40.5}$
$v = 6.4m/s$
