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, (pi)/3]x[π12,π3], where x is in meters?

1 Answer
May 31, 2017

The work is =179.75J=179.75J

Explanation:

The work done is

W=F*dW=Fd

The frictional force is

F_r=mu_k*NFr=μkN

N=mgN=mg

F_r=mu_k*mgFr=μkmg

=4(5+tanx))g=4(5+tanx))g

The work done is

W=4gint_(1/12pi)^(1/3pi)(5+tanx)dxW=4g13π112π(5+tanx)dx

=4g*[5x-ln|cosx|)]_(1/12pi)^(1/3pi)=4g[5xln|cosx|)]13π112π

=4g((5/3pi-ln|cos(1/3pi)|)-(5/12pi-ln|cos(1/12pi)|))=4g((53πlncos(13π))(512πlncos(112π)))

=4g(5/4pi+ln2+ln(cos(1/12pi))=4g(54π+ln2+ln(cos(112π))

=4g(5/4pi+ln2(cos(1/12pi)))=4g(54π+ln2(cos(112π)))

=4g*4.59J=4g4.59J

=179.75J=179.75J