Suppose a 5.00 kg box starts from rest and slides 2.50 m down a ramp. The ramp makes an angle of 30.0° with the horizontal. The coefficient of kinetic friction between the box and the ramp is µk = 0.436. Determine the work done on the box by the friction force between the box and the ramp.

The workdone by the friction force is

Explanation:

From the question we are told that

     The mass of the box is

      The distance it slides

     The angle made by the with the horizontal is

     The coefficient of kinetic friction is

 Workdone by frictional force is mathematically represented as

Now        

the cos is because the force is acting in horizontal direction and from the the question we can deduce that to resolve the force acting on the box horizontally we need to use cos

Substituting we have

Substituting value we have that

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.