A box is pulled along a level floor at a constant speed by a rope that makes a 45 degree angle with the floor. The box weighs 100N. The coefficient of sliding friction is 0.75. The normal force exerted on the box by the floor is?

Answer 1

M*g = 100 N.

Fn = 100*Cos0 - Fap*sin45 = Normal force
Fn = 100 - 0.707Fap

Fk=u*Fn = 0.75(100-0.707Fap)=75-0.53Fap

Fap-Fk = M*a
Fap-75 + 0.53Fap = M*0 = 0
1.53Fap = 75
Fap = 49 N. = Force applied.

Fn = 100-0.707Fap = 100 - 0.707*49 = 65.4 N. = Normal force.