8.-4 points SerCP10 5.P.018.WI My Notes Ask Your Teacher A man pushing a crate o

Question

8.-4 points SerCP10 5.P.018.WI My Notes Ask Your Teacher A man pushing a crate of mass m= 92.0 kg at a speed of v=0.875 m/s encounters a rough horizontal surface of length 0.65 m as in the figure below. If the coefficient of kinetic friction between the crate and rough surface is 0.357 and he exerts a 300 N on the crate. constant horizontal force of (a) Find the magnitude and direction of the net force on the crate while it is on the rough surface. magnitude directionSelect (b) Find the net work done on the crate while it is on the rough surface. (c) Find the speed of the crate when it reaches the end of the rough surface. m/s Need Help? Enan Euen"

Explanation / Answer

applied force F = 300 N

along vertical

net force = 0

n - mg = 0

normal force n = mg

frictional force fk = -uk*n

frictional force fk = -uk*m*g = -0.357*92*9.8

along horizontal

net force = F + fk = 300 - 0.357*92*9.8 = -21.9 N

part(a)

magnitude = 21.9 N

direction opposite ( -x axis)

======================

part(b)

work = Fnet*l = -21.9*0.65 = -14.24 J

================

part(c)

from work energy relation

net work = change in kinetic energy

Wnet = (1/2)*m*(vf^2 - vi^2)

-14.24 = (1/2)*92*(vf^2 - 0.875^2)

vf = 0.675 m/s <<<-----------ANSWER

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