posted by Sarah .
A taut string connects a 5-kg crate to a 12-kg crate (see figure below). The coefficient of static friction between the smaller crate and the floor is 0.573; the coefficient of static friction between the larger crate and the floor is 0.443. Find the minimum horizontal force required to start the crates in motion.
Wc = m*g = 5kg * 9.8N/kg = 49 N. = Wt.
Fs = u * Wc = 0.573 * 49 = 28.08 N. =
Force of static friction.
Wc = m*g = 12kg * 9.8N/kg = 117.6 N.
Fs = 0.443 * 117.6 = 52.1 N.
Fap-Fs1-Fs2 = m*a.
Fap-28.08-52.1 = m*0 = 0
Fap-80.2 = 0
Fap = 80.2 N. = Force applied.