as the slip increases, the current on the preposition to stay will decrease & as roughness of a surface increases , friction will increase ->  as the roughness of a surface increases, the resistance on the object to move will increase  as the smoothness of a bottom increases, the current on the preposition to stay will decrease & wood has a smooth surface & carpet has a rough surface -> the resistance on the object to move on the carpet will be larger than on the wood the resistance on the object to move on the carpet will be larger than on the wood  the resistance on the object to move on the carpet will be larger than on the wood & a element truck is a mean of preposition -> the resistance on the toy car object to move on the carpet is larger than on the wood the resistance on the toy car object to move on the carpet is larger than on the wood  the resistance on the toy car object to move on the carpet is larger than on the wood & as the current on the preposition to stay increase, the preposition will stay slower -> the toy car will move slower on the carpet than on the wood