A curved lake in a mapping

 

I love the panoramic function on the camera. It must simehow be mapping from curved space onto a flat plane, like the way that the globe gets distorted when mapped onto a flat sheet. You can get away with it for small sections of the globe but trying to represent the whole globe on one flat sheet leaves it distorted. Here Wastwater was straight when I was looking at it but now looks distinctly curved.

Arch dam at Seathwaite Tarn

 

Seathwaite Tarn was turned into a reservoir for Barrow over a hundred years ago. The dam is actually curved - seen behind the spillway in the photo above. Most dams I've seen are straight. This one has its curve facing the water. It occurred to me that an arch is a strong shape because the weight of stone above an arched window pushes the arch blocks into each other, locking them. Here, it is the water pressure that does that job. Turns out this type of dam has a name: an arch dam. It is neatly summarised by The British Dam Society who say that this type is rare in the UK because it needs strong rock foundations, presumably to be able to push back on the blocks that make up the dam. That is the case here.

How long was the adit at Seathwaite Tarn Mine?

 

In his book Mining in the Lake Counties, W T Shaw explains that you can guess the length of a tunnel from the volume of rock that has been removed. There is an impressive spoil heap at the entrance to the now blocked up adit - Wainwright's chapter on Grey Friar has a picture of what it used to look like. I'm estimating the spoil heap to be 10m x 10m x 5m meaning 500 cubic metres of rock. If the tunnel was 1.5m high and 1m wide, that would mean a tunnel 300m long. I have been unable to find any information about this mine because it is not mentioned in Shaw's book.

Speed of water in the stream

 This small stream on the way down Buckbarrow had an interesting feature. As water hit a shallow, weed-infested section at A, bubbles formed. They stayed until B. I timed several. It took around 3 seconds to go from A to B. Closer inspection wit walking poles suggested about 3 metres long so the speed would be 1m/s through this section.

Deceleration at Swirls

 Deceleration is a word rarely seen on road signs. Acceleration, the rate of change of velocity, is a vector. That means it can have any direction. Since it is usually measured along a line like a road, it is given a positive value if the velocity is increasing or a negative value if the velocity is decreasing. This negative value for acceleration is called deceleration. Clearly if you were waiting in the lane next to the sign, you would have no rate of change of velocity so would not be decelerating and would have no business in that lane.

                                       

Is it possible to move 730kg?

I have been thinking about the result of my calculation yesterday that the mass of the roundabout was 730kg. I have translated into hundredweight and it is about 14cwt. That is the mass of a smallish tenor bell in a bell tower which is moved by a wheel about the size of the roundabout. It sounds feasible the calculation is in the right ball park.
 

Trying to find the mass of the roundabout

 I was back on the roundabout. I timed myself as 7 seconds per rotation near the centre (say 0.5m from axis) and 8 seconds when I was about 1.5m away.

The movement should involve conservation of angular momentum. I have added my point moment of inertia to that of the roundabout, which I have taken to ne a disc of radius 1.5m. The result is a mass of 730kg for the roundabout. It might be a bit high but is not totally unrealistic.