有關摩擦力嘅問題(十萬火急!)(15點)

There should be plenty:

Walking, friction between shoes and floor
Brakes on vehicles
Car clutch
Rubbing of both hands to produce heat in cold weather
Striking a match to ignite it.
Writing using a pencil.

You could find more on the web.

THX!唔該晒你地!

2015-04-28 18:46:30 補充：
今日交咗，唔該晒知識長!

你可以行得走得，揸得住部手機就是。

http://zhidao.baidu.com/question/43416905.html