Question

A book with a mass of 1350 g is sitting on a desk. The ukf between the book and the desk is .45 and the ukf between the book and the desk is .30.
a. how much horizontal force is required to start the book moving across the desk?
b. Once it starts moving, what is the acceleration of the book?
c. If we want the book to move at constant velocity, how much do we need to reduce our original applied force.

Answer 1

a. M*g = 1.35 * 9.8 = 13.2 N. = Wt. of book. = Normal force(Fn).
Fs = us*Fn = 0.45 * 13.2 = 5.95 N.
F-Fs = M*a. F = Fs+M*a = 5.95+M*0 = 5.95 N.

b. Fk = uk*Fn = 0.30 * 13.2 = 3.96 N.
F-Fk = M*a. a = (F-Fk)/M.

c. Fap-Fk = M*a.
Fap = Fk+M*a = 3.96 + M*0 = 3.96 N. = Force applied.
Reduction = 5.95-3.96 =