Question #87f21

1 Answer
MetaPhysik
Feb 13, 2018

#K =[Fcostheta-mu(mg-Fsintheta)]d#

Explanation:

Use work-energy principle:

#W_"net" = DeltaK#

#vecF_"net"*vecd =K-0#

#K = vecF_"net"*vecd #

Because the sheeps is pulled a distance horizontally, meaning the net force is in the direction only, as components in the vertical (y) direction canceled out.

#K = vecF_"net"*vecd = F_"net"d #

The net force is the difference between the horizontal component of F and the friction counting the motion:

#F_"net"=F_x-f_k = Fcostheta-mu_kN#

Note: #N !=mg# because both the normal force and the vertical component of F are lifting the sheep such that

# Fsintheta+N=mg rArr N= mg-Fsintheta#

#therefore K =[Fcostheta-mu(mg-Fsintheta)]d#

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