(b) Since, $m_{2}$ moves with constant velocity
[image:7_image136.emf]
$\therefore\ f_{2} = m_{2}g$
$f_{2} = 8 \times 10 = 80$N
Since, boy of mass $m_{1}$ moves with acceleration $a = 2ms^{- 2}$ in upward direction
[image:7_image137.emf]
$\therefore f_{1} = m_{1}g = m_{1}a$
$\therefore f_{1} = m_{1}g = m_{1}a$
$= 10 \times 10 + 10 \times \ = 120$ N