$5.$A copper block has dimensions $1$cm x $2$cm x $4$cm A force of $0\mathrm{.}10$N will pull the block along a table surface at a steady speed if the $1$cm x $4$cm side is face down on the table. What force will be needed to pull the same block along when its $2$cm x $4$cm

side is face down?

$($b$)$Why are there no units attached to values of