A boat of area 10 m^2 floating on the surface of a river is made to move horizontally with a constant speed2m/sby applying a tangential force. If the river is 1m deep and the water in contact with the bed is stationary , find the tangential force needed eta_(H_2 O) = 0.01poise

A boat of area 10 m^2 floating on the surface of a river is made to mo

1.	A boat of area 10 m^2 floating on the surface of a river is made to move horizontally with a constant speed2m/sby applying a tangential force. If the river is 1m deep and the water in contact with the bed is stationary , find the tangential force needed eta_(H_2 O) = 0.01poise
Answer» Solution :Velocity gradient `=(2m//s -0)/(1m-0) = 2s^(-1)` , from , Newton.s law of viscous force, `F_v = eta_A (dV)/(dy) = (10^(-2) xx 10^(-1) SI) (10m^2) (2s^(-1)) = 0.02 N` To keep the boat moving with CONSTANT velocity , net force on it must be made zero. Therefore, we need to APPLY 0.02 N in the DIRECTION of motion.