Question

An object with a mass of `6 kg` is pushed along a linear path with a kinetic friction coefficient of `u_k(x)= 1+cscx`. How much work would it take to move the object over #x in [(3pi)/4, (7pi)/8], where x is in meters?

Answer 1

The work is `=66.21J`

Explanation:

`"Reminder : "`

`intcscxdx=ln|(tan(x/2))|+C`

The work done is

`W=F*d`

The frictional force is

`F_r=mu_k*N`

The coefficient of kinetic friction is `mu_k=(1+csc(x))`

The normal force is `N=mg`

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

`F_r=mu_k*mg`

`=6*(1+csc(x))g`

The work done is

`W=6gint_(3/4pi)^(7/8pi)(1+csc(x))dx`

`=6g*[x+ln|(tan(x/2))|]_(3/4pi)^(7/8pi)`

`=6g(7/8pi+ln(tan(7/16pi)))-(3/4pi+ln(tan(3/8pi))`

`=6g(1.126)`

`=66.21J`