An object with a mass of 6 kg6kg is pushed along a linear path with a kinetic friction coefficient of u_k(x)= 1+5cotx uk(x)=1+5cotx. How much work would it take to move the object over x in [(pi)/12, (3pi)/8]x[π12,3π8], where xx is in meters?

1 Answer
Apr 3, 2018

The work is =428.1J=428.1J

Explanation:

"Reminder : "Reminder :

intcotxdx=ln(|sinx|)+Ccotxdx=ln(|sinx|)+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=(1+5cotx)μk=(1+5cotx)

The normal force is N=mgN=mg

The mass of the object is m=6kgm=6kg

F_r=mu_k*mgFr=μkmg

=6*(1+5cotx)g=6(1+5cotx)g

The work done is

W=6gint_(1/12pi)^(3/8pi)(1+5cot)dxW=6g38π112π(1+5cot)dx

=6g*[x+5ln(sin(x) ] _(1/12pi)^(3/8pi)=6g[x+5ln(sin(x)]38π112π

=6g((3/8pi+5ln(sin(3/8pi))-(1/12pi+5ln(sin(1/12pi))=6g((38π+5ln(sin(38π))(112π+5ln(sin(112π))

=6xx9.8xx7.28=6×9.8×7.28

=428.1J=428.1J