WORK AP 1 chapter 6: section

WORK  The product of the magnitude of the displacement times the component of the force PARALLEL to the direction of motion.  Scalar but can be negative or positive (lose or gain)  W=F”d =Fdcos Ө  Ө is the angle between the force and the direction of motion.  Units are Newton-meter (Nm)= Joule (J)

WORK CAN BE  Done by the object (-W)  Done on the object (+W)  Done by a specific force (must name it)  Done by a Net force

A PERSON PULLS A 50 KG CRATE 40 M ALONG A HORIZONTAL FLOOR BY A CONSTANT FORCE OF 100N ACTING AT A 37°ANGLE. THE FLOOR IS ROUGH AND EXERTS A FRICTIONAL FORCE OF 50N. Find the work done by each force. Wg done by gravity =mgdcos Ө = 0 WN done by FN =Fndcos Ө = 0 WA done by person =Fadcos Ө= 100N(40m)cos 37 =3200J Wf done by friction =Ffdcos Ө= 50N(40m)cos180 = -2000J FN Ff Fa Fg

NET WORK ON CRATE Wnet= sum of all work =0J + 0J +3200J J =1200 J OR Wnet= Fnetd =(Fa-Ff)d =(100cos37-50)(40m) FN Ff Fa Fg

FORCE VS DISPLACEMENT Work is the area under the curve. F” (N) d (m) A=length*width=F”d=W A=1/2*base *height =1/2dF” =-W A=1/2(p+q)h trapezoid