A 400-kg bear grasping a vertical tree slides down at constant velocity. What is the friction force that acts on the bear?

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Answer 1 · 2017-07-21T08:14:58

#f_k=3920sintheta " N"#

400Kg bear slides down at constant velocity

In order to velocity to be constant, the net force must be zero.

Since that constant velocity = zero acceleration

#F_"net"=ma=m(0)=0#

In order to balance the force due to gravity, the frictional force must be of the same magnitude as it.

#F_"net"=F_"xg"-f_k=0#
#f_k=F_"xg"#

You said slide down, there must be an incline.

The horizontal force acting down and parallel to the surface of the incline is:

#f_k=mgsintheta#
[where #theta# is the angle of inclination with repect to #x#-axis.]

#f_k=400(9.8)sintheta#

#f_k=3920sintheta " N"#