This took me a short while to figure out, but I am still not entirely sure if this is correct, this is just from my basic understanding of Newtons Second Law of Motion.
You have a 4kg cart with a force of 20N acting on it.
The formula for working out the acceleration is.
a=Fnet÷mass
Substitute in the information.
a=20N÷4kg
Now you solve it to give you.
a=5m/s
So now what you should be able to do is figure out that after 10 seconds the cart travelling at 5m/s would have travelled 10 metres.
This is achieved by finding out how many 5's go into 10 which is 2.
So you do 5×2 which equals 10.
The 4kg cart has travelled 10 meters in 10 seconds with a force of 20N acting upon it.
I hope that this has helped you.