Science experiment -Forces

Question- Does covering a car ramp with different materials ( cloth, bubble wrap, paper) influence whether the toy car will go faster or slower down the ramp?

Firstly, we predicted and recorded what we thought would happen when we used different materials to cover the ramp. Then, we did a fair test and timed each trial. We found that the car moved fastest when the paper covered the ramp and the car moved much slower when bubble wrap covered the ramp.