I'm having trouble calculating the work done by friction over a surface. Here is a picture I've drawn of my problem:
I'm tasked with finding the work done on the box (which has a mass of 6 kg) after it goes over a surface with friction. The initial velocity is 14 m/s.
I'm aware work by friction would be equal to $Fd$, but the formula for friction is $\mu_kv$. As the net force is the friction force, I don't know how to find work by friction if the friction force varies as the box slows down. How do I find this?
Edit: Sorry, I for some reason thought the friction force was given by $\mu_kv$, when it should really be $\mu_kN$. That's probably why it wasn't making sense. I assume the work by friction would then just be $\mu_kNd$?