posted by nuwan .
The coefficient of static friction between a block and a horizontal floor is 0.40, while the coefficient of kinetic friction is 0.15. The mass of the block is 5.0 kg. A horizontal force is applied to the block and slowly increased. (a) What is the value of the applied horizontal force at the instant that the block starts to slide? (b) What is the net force on the block after it starts to slide?
Wb = mg = 5kg * 9.8N/kg = 49 N. = Wt. of block.
Fb = 49N @ 0 Deg.
Fp = 49*sin(0) = 0 = Force parallel to
Fv = 49*cos(0) = 49 N. = Force perpendicular to floor.
a. Fn = Fap - Fp - 0.4Fv = 0.
Fap - 0 - 19.6 = 0.
Fap = 19.6 N.
b. Fn = Fap - Fp - 0.15Fv.
Fn = 19.6 - 0 - 7.35 = 12.25 N.