a$)$ How large a horizontal force is required to give a $8$ kg block an acceleration of $5$ms$2$ across a floor if the coefficient of sliding friction between the block and the surface is $0\mathrm{.}25$ b$)$ What mass M hanging from a cord attached to this block and passing over a small fricionless pulle will produce this acceleration? a$)$ b$)8$ kgF $8$ kg