One of the problems with living in the country is that things grow. That doesn't sound like much of a problem but when they grow on the roof of your house it is. Last week I begun the task of removing the moss from our roof. Quite a job I can tell you. I'm not sure if its really a good thing either since I seem to scrubbing away a lot of roof tile in the process. To get onto the roof I use a ladder so I have to be careful how I angle it. The problem is that it might be fine when you start climbing but as you get higher the normal force between the ladder and wall gets bigger, this has to be balanced by the friction at the bottom and if this isn't enough the ladder will slide down the wall. Torques will probably be part of the new engineering physics option so student will be able to understand all about ladders against walls again. Just think of all the potential accidents that will be prevented due to this.