Predict the motion of a cart (with friction)

You have ALREADY done this experiment:

set up a track on your table so that one side sits 5.0 cm higher than other
let the cart roll 80 cm from rest

If there were no friction, what should the acceleration have been? What was the actual acceleration you measured?

Based on your measurements,

compute the force of friction on the cart
determine the "coefficient of rolling friction" between cart and track

Fine. But ... is this correct?

One way to find out is to change the angle of the track and repeat the experiment. If friction really behaves as described in class and in your textbook, then NOW you should be able to predict the motion of the cart accurately. Let's see if you can....

change the tilt of your track so that one end is only 3 cm above the other end (instead of 5 cm)
predict the time it should take for the cart to roll 80 cm; be sure to include friction as necessary
write your calculations and prediction neatly on a piece of paper, and hand it to an instructor

Now let the cart roll, and see if you were right!