Crate being pulled with and without friction

[eioous]

Homework Statement

A 51.0 kg crate, starting from rest, is pulled across a floor with a constant horizontal force of 250 N. For the first 10.0 m the floor is frictionless, and for the next 10.0 m the coefficient of friction is 0.20.

What is the final speed of the crate after being pulled these 20.0 m?

The Attempt at a Solution

I'm just really not sure what to do or where to start on this problem. please help.thanks

 

[needlottahelp]

I'm not to sure about this but I think you can divide it into two parts first. Find the Vf of the first 10.0 m then use that as the Vi for the other 10.0 m with friction and find the Vf again. That should give you the answer I believe.

 

[athenos]

Use Newton's 2nd law and vector summation to find the acceleration of the crate for both parts. For the first part the net force is just 250n, and for the second part it is 250n - Friction. Then use kinematics.