Question

A large wooden plate of area 10 m2 floating on the surface of a river is made to move horizontally with a speed of 2ms by applying a tangential force if the river is 1 m deep and the water in contact with the bed is statiknary

Answer 1

Answer:

velocity gradient is 2s−1

C

force required to keep the plate moving with constant speed is 0.02N

Velocity gradient=ΔhΔv=1m2m/s=2s−1

F=ηAΔhΔv

=(10−3)(10)(2)

=0.02 N