Question

Find the force required to start motion.

Answer 1

more than 40 . because friction is only 40 and if force applied is also 40 than it will remain at rest only

Answer 2

here as body is not moving.. we will not use μk
so,...
F=(μs)mg =frictional force
=0.2×20×10
=40N
as just frictional force has to be overcome here to start motion ....
thus F=40N

hope it helps you.... :)....