Posted by shadad on Sunday, February 5, 2012 at 7:26am.
to move a crate across a rough floor ,you push on it at an angle of 21degrees below the horizontal. find the force necessary to star the crate moving ,given that the mass of the crate is32kg and the coefficient of static friction between the crate and the floor is o.57.

physics  drwls, Sunday, February 5, 2012 at 8:22am
The normal (downward) force on the floor is M*g + F*sin21. (F is the applied force). To start the crate moving, the force F must satisfy the inequality:
F*cos21 >or= (M*g + F*sin21)*0.57.
0.9336 F >or= 178.8 N  0.2043F
1.138F >or= 178.8 N
F >or= 157.2 N