Posted on 10 April 2011 at 19:43h

A week ago the weather was at last good enough to start the Friday rock climbing activity so I took a group of students to the cliff situated a 5 minute walk from the college campus. When we got there I was shocked to see that a large part of it had fallen down. Not the bit we climb on but rather too close for comfort. What happens is; water that runs through cracks in the rock freezes in the winter, as it turns to water it expands and pushes the rock apart. When the ices thaws in the spring the rocks fall down. As a result we can no longer climb on the cliff so I must find a new one for the climbing activity. Luckily there is rock everywhere in Norway and this weekend  have been developing a cliff only a couple of minutes from my house (closer than the old one). Most of the preparation involves scrubbing the rock with a wire brush, removing grass and trees and placing bolts. The photo shows a bolt anchor. The bolts shouldn't be placed too far apart or the force exerted on each of them will be substantially more than the weight of the person hanging on the rope. Actually the force is twice the weight of the person hanging on the rope since there are two people one hanging and the other holding the rope. That's of course assuming they are hanging on the rope which on this cliff they won't be since its not vertical. Some interesting physics here, maybe I should take my class rock climbing?