A 550 N crate rests on the floor. How much work in joules is required to move it at constant speed 7.0 m along the floor, against a friction force of 150 N?

2 answers

Fap-Fc-Fs = M*a.
Fap-550-150 = M*0 = 0, Fap = 700 N. = Force applied.

W0rk = Fap*d = 700 * 7.0 = 4900 J.
Correction: Fap-Fs = M*a.
Fap = M*0 + 150 = 150 N. = Force applied.

Work = Fap*d = 150 * 7 = 1050 J.