Component of weight on a ploughing boulder

 I've posted about ploughing boulders before. This is a very good example on the slopes above Tray Dub in Langstrath.

The pole is 90cm long. The estimated dimensions of the boulder are 2m x 1m x 1m. Density of volcanic rock like this is 2500 kg per cubic metre so mass is estimated at 5000 kg. This is a steep slope to walk on; that usually means 30 degrees. Thus component of weight down the slope shown is 5000 x g x sin(30) = 25kN to 2sf. Most of the time friction is enough to hold it but some winters the freeze-thaw means friction must be less than this.