A block of mass 10 kg is put gently on a belt-conveyor system of infinite length at  $\text{t}=0\text{\hspace{0.17em}sec},$ which is moving with constant speed  $\text{2}0\text{ m}/\text{sec}$  rightward at all time, irrespectively of any situation by means of a motor-system as shown in the figure. A constant force of magnitude  $\text{15 N}$   is applied on the block continuously during its motion.