Hydraulics at Threlkeld Quarry

We went to Threlkeld Quarry to see a steam digger. Steam driven pistons can only move in a straight line. But the hydraulics on this old JCB are an improvement. Water is incompressible. The molecules are so close together that there is no space between them into which they can be squashed. This means that water transmits pressure. If you push on one side, you also push on the other side. Water pressure acts equally in all directions - up and down and sideways. So pushing on one end of the hydraulic fluid in the black pipes means that a push is generated at the other end as well to move the digger arm. The black pipes go round the corner but the pressure is still transmitted because of the way that pressure acts in all directions.

Foyers hydro-electric scheme

Foyers is a very small community on the south side of Loch Ness. Loch Ness has very steep sides and there is an amazing waterfall at Foyers. The energy from it was harnessed for hydroelectricity for the first aluminium smelter in the UK. It was so long ago that Lord Kelvin was involved.

 These are the old smelter buildings. Production ceased in the 1960s. In 1974 some of the plant was reopened as a hydroelectric power station.

 The water flows in from the river above the village. It is a long way up the hill from the lochside factory.

It is said to be a small station at 5MW but Glenridding hydro in Cumbria is only 1/10th the size at 500kW. Also compare it with 200MW at the old Chapel Cross nuclear power station that I can see from my house. It seems quite big. But a lot of wind farms are much bigger. Foyers has a 108m drop from top to bottom. Let's say that the generator runs on the loss of gravitational potential energy mgh. Power = energy changed/time taken. Thus power = dm/dt x gh. Mass flow rate dm/dt thus calculates out at about 4.5 tonnes per second. That's about 25 baths of water every second. Not inconceivable. It may be higher because if the 5MW is the electrical output there will be losses in the generator mechanism.

Not the Loch Ness Monster

When we were at Loch Ness 2 years ago I remember being really impressed by the ability of a boat wake to survive on the water. It was at least 5 minutes after the boat had gone that day. This time, I spotted this wake as we were driving along the south shore. The cruise boat had long gone. Compare this with the pictures in the newspaper from the month after our last visit. http://metro.co.uk/2013/08/26/do-new-pictures-from-amateur-photographer-prove-loch-ness-monster-exists-3938074/

 

 We went on the same cruise ship. It is a large catamaran that sends out a big Kelvin wake - I've blogged about that before. http://wigtonphysics.blogspot.co.uk/2013/11/kelvin-wake-on-walla-crag.html

 The wake is made of the traditional V-shape but is also split into individual wavelets. As the boat turns across its own wake, from certain angles these wavelets can look like a series of humps.
                                     
This explains some of the claimed sightings in my own mind but not the "neck-sticking-out" ones.

Harwell Campus Open Day in Oxford

If you want to see inside one of the most impressive scientific research establishments in the country, it will be open to the public on SATURDAY 11 JULY 2015. Only problem for us is that it is a minimum 6 hour drive from Wigton. I went round the Diamond Light Source synchrotron a few years ago. They accelerate electrons up to such high speeds that they release X-rays when they turn a corner. The high energy X-rays are then used to probe the structure of molecules. Details are on this link http://harwellcampus.com/open-days/

No revision lessons on Thursday 21 May

There won't be any Sixth Form revision lessons on Thursday 21 May. I am going to a funeral.

Conglomerate above the Secret Cave

Climbing the hillside above the Secret Cave, I found this amazing rock. I thought it was made of volcanic bombs but it is actually a conglomerate. Transportation cannot have been far because the particles are so big and they are very angular. There hasn't been much bashing together of the rock fragments to round their outlines. Apparently it formed in a delta. The rock fragments are volcanic but it said to be a sandstone infill, which I'll need to check if I go again. I found a wonderful article about the development of the Scafell Volcano Caldera. This area was on the outer edge. http://jncc.defra.gov.uk/pdf/gcrdb/GCRsiteaccount289.pdf Looking at the rock, I suppose it does look more like water transport because of the density of the large fragments. Volcanic bombs probably wouldn't occur in this density in ash.

Rannerdale bluebells 2015

We finally managed to get to Rannedale in the bluebell season. It occurs to me that the same spectrum of sunlight falls on the bluebells, the yellow gorse and the green leaves. They are each doing something different with the light. I know that the leaves absorb the red and blue ends of the spectrum to use the energy for photosynthesis. The leaves reflect the green and this is what we see. The bluebells must reflect the blue end of the spectrum. Presumably they absorb the rest. The only alternative is that they transmit it and I saw no evidence of that. It got me thinking about the spectrum of daylight. To what extend are the colour wavelengths evenly transmitted to the Earth? How does the blue scattering of the sky affect the overall effect? I found this to start my thinking http://en.wikipedia.org/wiki/Sunlight

Not the runaway train

Here's the train going back down the hill at Threlkeld quarry. It was pointed out to me that the carriages would naturally keep rolling downhill once moving under gravity. There is friction between the wheels and the rails. This is equal to coefficient of friction x normal reaction force. There will be a large normal reaction force from such a heavy carriage. But provided the component of gravitational force is bigger than this, the carriages would accelerate downwards. The problem of friction brakes is that they get very hot if constantly applied and can burn out. A car's petrol engine can be run downhill in a low gear to have a braking effect but this is harder to do with a steam train although I have found articles about "countersteam" dynamic braking. It seems a complicated subject so more thinking needed.

Fluorescence in Threlkeld

The Mining Museum in Threlkeld is packed with wonderful information. I particularly loved this fluorescence exhibit. Atoms contain electron energy levels. Energy reaches the electrons in the lowest energy levels in the form of light photons. The energy is calculated from the frequency by E=hf. Ultra-violet is high frequency so each photon carries a lot of energy. It can skip over several energy levels. What goes up must come down, the electron falls back to its ground state. But it doesn't have to do it in one jump. It can bump back down the intervening levels in several jumps. As it does so, it releases photons of light. If it bumps down in the smaller jumps, the photons have a lower frequency - low enough a frequency to be visible to our eyes. This is actually how fluorescent tubes work - but more on that another time.

Altocumulus undulatus?

I took these photographs on the Lincolnshire coast. The wind was blowing from the land onto the sea. A bit of research suggests that the most likely cloud type is altocumulus undulatus.  http://en.wikipedia.org/wiki/Altocumulus_undulatus_cloud  The ribbed pattern is so regular that I was wondering whether it was a stationary wave pattern, but the whole pattern was moving across the sky. That suggests that the pattern was fixed when the clouds were formed. I haven't found a perfect explanation yet but they are talking about shear forces. Shear is tearing - forces pulling across something. The first picture, taken through a polarising filter, shows that the winds higher up were to some extent crossing each other because the ripple patterns are crossing each other.

Magnox in the museum

 The fuel rod on the right above is a Magnox fuel rod. This is quite a distinctive design.

It seems that they used unenriched uranium metal in this type of British fuel rod. The name comes from the casing which is made of a magnesium oxide and aluminium alloy because it would not oxidise in the extreme conditions in the reactor. The nuclear power station at Wylfa on Anglesey thatI saw last year is the last remaining Magnox station. Fission of the uranium-235 nucleus results in smaller nuclei called fission fragments. A uranium nucleus is only stable because it has far more neutrons than it should to help hold the nucleus together. Small nuclei like carbon or oxygen have equal numbers of protons and neutrons. The neutrons provide extra strong nuclear force to overcome the electrostatic repulsion of the protons. The electrostatic repulsion works over a much larger range so in a big nucleus more neutrons are needed because the effect of their strong nuclear force is only local. These extra neutrons are not needed in the smaller fission fragments. The only way to lose them is by beta-minus decay. The neutron decays into a proton, releasing an electron (from the nucleus!) and an anti-neutrino. The rate of decay is high. Each decay releases energy as heat. Hence the spent rods need to be put into cooling ponds until this initial fast decay has spent its energy. One problem with Magnox was that the fuel casing reacted with water. Magnesium does react with hot water! One final thing to note is the large surface area of the fins used to help the rods to lose thermal energy more efficiently.

Doppler Effect in the bath

Mrs B bought me a balloon powered boat. It has holes in the bottom and two at the back. The air through the bottom is supposed to make a sort of hovercraft effect and the two at the back will propel it along. I haven't yet had the best from it but the bottom picture showed that it can demonstrate the wave pattern associated with the Doppler Effect. The whole system seems to create circular ripples but the boat was moving from right to left. It moves away from the ripples on the right, increasing the wavelength and thus decreasing the frequency. It moves into the ripples on the left, decreasing the wavelength and increasing the frequency.

Lincs offshore wind farm

Here are 2 views of the same colossal offshore wind farm -first looking north from Gibraltar Point and second looking south from Mablethorpe. I estimated about 70 turbines. I looked it up on the excellent wikipedia offshore wind farms page. It consists of 75 turbines made by Siemans. They are 100m high to the rotor hub and the diameter of the blades is 120m. Each is 3.6 Mw so the wind farm is rated as 270 MW. Hartlepool nuclear power station is 1300MW so about 4 of these would be rated the same. Except that the capacity factor isn't listed. this is normally about 0.3 so you'd need 3 times as many on average. They are expected to last about 40 years but that is about the same as a nuclear power station. It cost £1 billion to build. Nucleat clean up is expensive. I need to find pout how they wire up the 75 turbines. Are they series or parallel? Solar cells are a mixture of the two where series increases the emf and parallel reduces the effect of internal resistance.

Tracking the sunrise in Mablethorpe

The structure above is on the seafront at Mablethorpe in Lincolnshire. I thought it was a sundial. It does indeed work by projecting a shadow of the Sun, but it has been set up to record the position of the Sun at sunrise on specific dates throughout the year. So it's like a latter day Stonehenge. The lines on the pavement are labelled with dates.

The line furthest right in the top photograph is labelled "True South". In other words, that is the position of the Sun at midday (allowing for the analemma issue). Summer Solstice is the line nearest to it, and Winter Solstice is the line furthest away. This because on the Summer Solstice, the sun rises the furthest north of any day as it has further to go across the sky to reach south by midday. The Sun is out for more hours on that day. Hence its shadow at sunrise must be closest to the south. It is almost counter-intuitive and it took me a while to understand it.

Back to Roger Bacon

I found this in the Technical Museum in Berlin. Roger Bacon is quoted as saying that it will be possible to make flying machines in which humans can sit.They will have artificial wings, like a bird in flight. Either perceptive or lucky for 1285. I visited his memorial in Oxford last October and wrote a post about it. Since then, the Westgate car park has been demolished to extend the shopping centre. I hope they preserve the memorial. The site is a mess at the moment.

Physics and the new Weston library

This was the outside of the New Bodleian library in Oxford 3 years ago. I loved the hoardings and spotted a couple of Physics related letters in their alphabet.

 

It's been finished! Sadly we didn't have time to go in on this visit but next time...

Beckley mast - plane polarised TV waves

Here's the view from Debenham's café in Oxford. Between  the church tower and the tree you might just be able to pick out Beckley mast, the TV transmitter for Oxford. It is a primary transmitter and the TV electromagnetic waves from it are horizontally plane polarised. The TV aerials on houses will need to have the metal rods in the horizontal plane to detect them. There will be places hidden by hills where you cannot see the mast. TV waves probably have too short a wavelength to diffract round the hills and into the valleys - I need to check this. So they use repeater antennae called relay stations. These take in the signal from Beckley and re-broadcast it into the valleys. The re-broadcast signal is sent out with vertical polarisation. I have not seen this said anywhere, but I imagine that is so that there is no interference between the two versions of the same signal. I found a marvellous website about all of these issues http://www.aerialsandtv.com/aerials.html so expect more!

Centre of gravity on Cornmarket

We saw this entertainer on Cornmarket in Oxford. This is obviously a very simple trick: you need to get your centre of gravity over the rope and then you balance... Very difficult in practice. First there is the distinction between centre of mass and centre of gravity. It depends what you are doing. If you are trying to accelerate something, then inertial mass becomes important and it is the centre of mass that you want. Here, we are interested in the weight, so centre of gravity will be a more sensible usage although I think they are in the same place. If the centre of gravity is not above the rope, there will be a perpendicular distance from the rope, which will act as a pivot, and the line of action of the man's weight. There will thus be a resultant torque which will make him spin one way and fall. The balancing act involves producing a movement to make an equal and opposite torque every time you wobble slightly.

Hareshaw Linn: minimising potential energy

Hareshaw Linn is a waterfall in an impressively gothic ravine near Bellingham in Northumberland. This picture doesn't really do it justice. Solar energy lifted the water up from the sea by evaporation, doing work against gravity and giving it a lot of gravitational potential energy. Then the water begins to try to minimise its potential energy. It always seeks out the lowest point. This waterfall is an impressive example of it doing that. Yet even on the waterfall itself, there were certain channels that must have lower potential energy than other parts as the water sticks to certain routes across the fall.

Crumple zone

The engine compartment at the front of the car is designed to crumple up in the event of a crash. This means that it takes a longer time to come to a standstill. The same momentum is lost over a longer time so we say that the rate of change of momentum is reduced. By Newton's Second Law, a lower rate of change of momentum means that the force of the crash is smaller so you are less likely to get hurt.