An object with a mass of 4 kg4kg is pushed along a linear path with a kinetic friction coefficient of u_k(x)= 5+tanx uk(x)=5+tanx. How much work would it take to move the object over #x in [(-pi)/12, (5pi)/12], where x is in meters?

1 Answer
Jun 25, 2018

The work is =359.5J=359.5J

Explanation:

"Reminder : "Reminder :

inttanxdx=ln|(cos(x))|+Ctanxdx=ln|(cos(x))|+C

The work done is

W=F*dW=Fd

The frictional force is

F_r=mu_k*NFr=μkN

The coefficient of kinetic friction is mu_k=(5+tan(x))μk=(5+tan(x))

The normal force is N=mgN=mg

The mass of the object is m=4kgm=4kg

The acceleration due to gravity is g=9.8ms^-2g=9.8ms2

F_r=mu_k*mgFr=μkmg

=4*(5+tan(x))g=4(5+tan(x))g

The work done is

W=4gint_(-1/12pi)^(5/12pi)(5+tan(x))dxW=4g512π112π(5+tan(x))dx

=4g*[5x+ln|(cos(x))|]_(-1/12pi)^(5/12pi)=4g[5x+ln|(cos(x))|]512π112π

=4g(25/12pi+ln(cos(5/12pi)))-(-5/12pi+ln(cos(-1/12pi))=4g(2512π+ln(cos(512π)))(512π+ln(cos(112π))

=4g(9.17)=4g(9.17)

=359.5J=359.5J