An object with a mass of 6 kg6kg is pushed along a linear path with a kinetic friction coefficient of u_k(x)= 2+cscx uk(x)=2+cscx. How much work would it take to move the object over #x in [pi/2, (7pi)/8], where x is in meters?

1 Answer
Jun 15, 2017

The work is =233.5J=233.5J

Explanation:

We need

intcscxdx=ln|tan(x/2)|cscxdx=lntan(x2)

The work done is

W=F*dW=Fd

The frictional force is

F_r=mu_k*NFr=μkN

The normal force is N=mgN=mg

The mass is m=6kgm=6kg

F_r=mu_k*mgFr=μkmg

=6(2+cscx)g=6(2+cscx)g

The work done is

W=6gint_(1/2pi)^(7/8pi)(2+cscx)dxW=6g78π12π(2+cscx)dx

=6g*[2x+ln|tan(x/2)|]_(1/2pi)^(7/8pi)=6g[2x+lntan(x2)]78π12π

=6g((2*7/8pi+ln|tan(7/16pi)|)-(2*1/2pi+ln|tan(1/4pi)|))=6g((278π+lntan(716π))(212π+lntan(14π)))

=6g(7/4pi-pi+1.61)=6g(74ππ+1.61)

=6g(3/4pi+1.61)=6g(34π+1.61)

=233.5J=233.5J