# A man of mass () is sitting in a train movingwith velocity  . He observe that a block of mass  is moving towards him with velocity . Then the kinetic energy of block w.r.t  man is (Assume )

$\frac{1}{2} m (v_1+ v_2) ^2$
$\\=\frac{1}{2} \times 5 \times [ 3+5] ^2 = 1/2 \times 5 \times 64\\ \\ =5 \times 32 = 160 J$