If you scrape one thing against another, the weaker material might scratch or even tear.
You can make a fair test for this. Here we use fabrics. The material you see is a cotton handkerchief. Test a piece of old jeans and try to work out why jeans are more hardwearing than a handkerchief even though both are made from cotton...
Playing time: 3 minutes. (For hints on using videos click here.)
