Cirrus cloud over Castlerigg Stone Circle

I spotted these clouds yesterday afternoon. Cirrus are very high - over 5km up in the atmosphere. It might be below -20 degrees Celsius up there. Thus they are made of ice crystals rather than water droplets. The winds are very strong at that height so the clouds are strung out and are shaped like commas. They form ahead of a warm front. Oncoming warm air is pushed up above colder air and condensation happened. The front arrived overnight. It did feel like a warm night to me.

Higgs Hunters

Zooniverse is a "Citizen Science" project that started life as Galaxy Zoo. A researcher at Oxford University realised that humans are better at classifying galaxies from photographs than computers. They asked people to help via the Internet and were overwhelmed by how successful it was. They have undertaken many similar projects. They have just launched one to help researchers at the Large Hadron Collider at CERN identify particle events on photographs that might lead to more evidence for the Higgs Boson. I had a go yesterday. There are instructions to help you. Some of the pictures are easier than others but you should have a go and help this wonderful project: http://www.higgshunters.org/

Solar System Christmas Tree at Caldbeck

There is a display of Christmas trees at Caldbeck church this weekend. I loved this Solar System design. What a brilliant idea! The star at the top of the tree is our Sun and the planets spiral round the tree in order. You can easily identify the Earth and red Mars along with Saturn in the pictures. I wasn't able to go myself so I don't know how they dealt with Pluto, which was relegated from full planet status some years ago. It spoils the mnemonic I used to use with classes: My Very Easy Method Just Speeds Up Naming Planets.

Water ball in Windermere

I spotted this feature outside a hotel in Windermere. Water trickles out of the top of the globe and down the sides. What made me stop and think was that the water stays at the surface of the globe even below the equator. You'd think that gravity would pull the water straight down as a waterfall from the equator, but the water stays stuck to the surface to continue its descent. The ball was not electrically charged. The outer surface of the water certainly experiences surface tension but is it this force that also holds the water onto the surface of the ball? Gravity continues to pull the water downwards but the force from the surface on the water must be stronger than the gravitational pull to stop it leaving the surface. My hypothesis is that if the flow rate were higher then the water would leave the surface at the equator.

Long exposure on Binsey

We climbed up Binsey in the dark. I was pleased that the long exposure on the camera was able to let in enough light to make any sort of picture. I put the camera on a tripod and used the timer to avoid knocking the camera because I'm guessing the shutter was open for several seconds. I need to come up with a strategy for measuring it. It is a time when the Charge Coupled Device CCD that is the light sensor comes into its own because it has a quantum efficiency of 70% compared to 4% for chemical films. That means that 70% of the photons are detected so they can operate in lower light intensities.

Archimedes Screw at Whinlatter

We enjoyed this at Whinlatter. It is an ancient type of water pump and such a wonderful technology. So how to do a thorough-going Physics analysis? The weight of the water holds it in the bottom of each section. You turn the handle and the walls of the screw apply a centripetal force to the water, pushing inwards on it. It is a complex example of centripetal motion because the water itself does not spin round. It has inertia so it tries to stay where it is and I suppose that the metal walls slide underneath it. The kinetic energy put in by you turning the handle is transformed into gravitational potential energy as the water finds itself in the next level of the screw. That's an outline of the ideas going through my head. I'm not yet convinced that I've put the parts together in a logical and forceful way.

Chilling with Ueli Steck

We went to hear the amazing Ueli Steck at Kendal Mountain Festival. If you've not come across him, watch this: http://www.wimp.com/eigerrecord/ He spends a lot of time in very cold places so as a tribute I took this photograph of my chilled fizzy beverage in the bar. Notice the condensation forming above the liquid level. That's water vapour in the air condensing back into liquid water. It made me think about the process in more detail. I'm thinking that the reduced temperatures slows the water molecules in the vapour so that the weaker electrostatic forces that keep water molecules together in a liquid. I'm thinking Van der Waals forces but a quick glance at the Internet suggests that it might be more complicated than that. A simple thing and I don't really know it!

V-pendulum at Whinlatter

 

I timed this swing in the play area at Whinlatter. It took 31 seconds for 10 complete swings, although I did time from the amplitude instead of putting a fiducial marker in the middle which will have slightly affected the accuracy. So 3.1 seconds for the time period. It looks really complicated with so many strings hanging, but I had a hunch that it would obey the equation for the simple pendulum using the vertical height up the middle to level with the top support. T=2pi x sqrt(L/g). It gives L, the vertical height, as 2.4 metres. That looked about right.

Pirate ship!

When I was in the Sixth Form, we were sent to escort a group of new Year 7s on a trip to Alton Towers, which had far fewer ride sin the those days. I tried the Pirate Ship and hated it. The trouble was that I knew I had to outlast the Year 7s, so I had to stay on 10 consecutive times. What was the big problem? I don't think that the forces were large. I'm estimating the radius as about 12m. Using the rapid repeat photograph mode on the camera, I estimate that the ship moved 1.2m in 0.3 seconds through its equilibrium position. That gives a maximum speed of 4 metres per second. So the centripetal acceleration will be vsquared/r = 16/12 = 1.3 m/s/s. That's nowhere near g. But the problem came at the top. For a split second you and the ship stop. The you are in free-fall against the barrier which I found unnerving!

When seagulls follow the trawler: bow waves

I was watching this fishing boat at Silloth and ended up thinking about the way that bow waves form at the front. The boat was moving at a steady speed on a reasonably calm sea. It was almost low tide so the current would have been small so it wouldn't be unreasonable to think of the sea water as stationary with a moving boat on it. So the front of the boat pushes on the water. Molecules in water are close together. You can't compress water very much. So the large mass of water in front of the boat (in tis case all the way to Ireland) gets in the way of the water that is being pushed forward by the boat. Hence the water mounts up. They will gain gravitational potential energy and will then try to lose that by falling. I think this will be why the wave them spreads out.

Year 10: Specific Heat Capacity using liquid nitrogen

I went to a lecture last week at which a piece of iron of mass 469 grams was placed in an insulated tub of liquid nitrogen. Liquid nitrogen boils at -196 degrees Celsius so a block of iron at room temperature (24 degrees Celsius) will seem stupidly hot to it. Thermal energy from the iron block went into the liquid nitrogen by conduction and made it boil.

 This next picture shows you a murky looking iron block below the surface of the liquid nitrogen.

The scales had been zeroed with the tub of nitrogen on top and then the block of iron was added so that the reading on the scales was 469.00 grams. As the liquid nitrogen boiled, nitrogen gas went off into the air and the reading on the scales went down. Here is the final reading.

Now the iron loses 200 Joules of thermal energy for every gram of nitrogen that goes into the air.

1. Calculate the mass of liquid nitrogen that boiled off into the air.

2. Show that 48064 Joules of energy must have gone out of the iron and into the liquid nitrogen to make that much boil away.

3. Use energy = mass x c x change in temperature  to calculate the specific heat capacity of the iron. (Hints: the iron cooled from room temperature to the temperature of liquid nitrogen, and you need to put the mass of the iron into kg to get a decent answer)

4. Look up the true value from the specific heat capacity. We were very close. Explain why that means we can say that the experiment was accurate and give a reason why it is impossible for this experiment to give a perfect answer.

Apples float and pears sink

I went to an excellent cookery demonstration last night. It was said that the way you tell the difference between apples and pears is that apples float and pears sink.  The Internet agrees. This picture shows what I found in my kitchen. The pear is a sweet desert pear. We are wondering if it is a cross with an apple. It is also quite ripe so maybe that makes a difference. Further research is required. Internet answers say that apples continue to "breathe in oxygen". That doesn't sound scientific to me. For a start, breathe is a word used for mechanical ventilation by lungs. Plants absorb gases by diffusion. Perhaps apples do continue to do respiration, for which oxygen would be needed. I will try to find an answer. But respiration would create carbon dioxide gas which would pass out by diffusion. I'm not convinced that the apple ends up pumped with oxygen but I'll try to find a definitive answer.

Things float in water if they are less dense than water. The pear is almost under water so it must be very close to 1 gram per cubic centimetre. The apple sits higher in the water.

Archimedes says upthrust = weight of water displaced. Since the volume of water displaced is almost equal to the volume of the pear, density is almost water. Upthrust has to equal 0.098kg x g.

Upthrust = 0.129kg x g but say 10% of the apple is above the water. Then perhaps the density is 0.9 grams per cubic centimetre.

Bass: how low can you go?

It was Rock Night last night. Thanks to those who came and to those who made it happen! I was looking at the bass bins. Speaker cones are meant to spread out the sound waves in all directions by diffraction. In other words, it would be bad if you could only hear the sound if you were stood directly in front of that speaker cone. What if you were slightly off to one side? Diffraction takes sound waves and makes them into semi-circular wavefronts going in all directions. But it works best if the size of the hole is the same as the wavelength. Take the stop speaker. Diameter is roughly 30cm. For waves, speed = wavelength x frequency. The speed of sound is roughly 330 m/s. If the wavelength is 0.3m, then frequency = 1100 Hz. I've never done the calculation before. That's a surprisingly high frequency for bass. The slightly smaller cones below will work best for even higher frequencies. So if you want to hear the very lowest frequencies best, you'd probably need to stand more or less in line with the speaker.

Sixth Form question: how far away is Blackpool Tower?

You might need to enlarge this picture to see Blackpool Tower!
Imagine a triangle that goes from my eye to the top of my little finger, down to the bottom of my little finger and then back to my eye. Show that the angle at my eye end is about 0.5 degrees. Then compare Blackpool Tower with my little finger and use similar triangles to work out how far away I was stood from Blackpool Tower. You might even be able to tell me where I was!

Sky Mirror at Nottingham Playhouse

Sky Mirror is a work of art by Anish Kapoor outside Nottingham Playhouse. It is a polished silver bowl. We'd say that the sky is at infinity as far as the study of Optics is concerned. That's because all the rays of light coming from the sky to the mirror will be parallel. Those hitting the top of the mirror are reflected downwards. Those hitting the bottom of the mirror are reflected upwards. Standing this far away, the rays coming down from the top cross over with the ones going up from the bottom and the picture is upside down. If the mirror is parabolic, there should be a single focal point. If you stand closer than the focal point, the rays don't cross and your reflection is the right way up.

The convex side was harder to see due to building works.

This diagram shows why the image is the right way up, because the rays never cross over.

You see a virtual image - you behind the mirror. If it is the same distance behind as you are in front, the fact that your brain thinks the rays get closer together behind the mirror makes you look smaller.

Of course, you can test all of this with a spoon.

 

The Border Stane - not for time travellers?

This lovely work of art is in the Newcastleton Forest very close to the border with England. I think it must be ones of the 7 Stanes of the eponymous cycle routes. You'll see that Jerusalem is carved onto the side facing England and Ald Lang Syn faces into Scotland. Both songs seem timeless and perhaps a little nostalgic - to do with human perception of time. Time famously only goes in one direction. They talk about the Arrow of Time. You can cross the border in either direction but time only goes forwards. Hence we can look back on Ald Lang Syn or on Ancient Time but we can't look forwards to know the future. You can look both ways through the hole in the monument but you can only look with certain knowledge in one direction for time. This means time is an odd quantity in Physics. Space (by which I mean direction) is symmetrical in a sense, but time isn't.

Cable-stayed bridge in Southport

This isn't a suspension bridge because the cables are angled and not vertical. On a suspension bridge, there are two parallel cables from shore to shore and then vertical cables hang down to hold the deck. Here, the cables provide a vertical component to hold up the bridge deck but there is also a horizontal component towards the support. This means that the material from which the deck is made needs to be more rigid than that for a suspension bridge. Its compressive strength must be greater. This isn't quite a classic cable-stayed bridge because it is actually anchored to the shore on the left. It is possible to have two halves of the deck hanging from a single central pillar because then the horizontal components pulling in towards the pillar from left and right can be made to balance with no need for an anchor on the banks.

Mechanical advantage above Loweswater

We found this piece of equipment near the Mosser road above Loweswater. I couldn't work out what it had been used for but it had a lovely example of a lever on the side.

You put a small effort into pulling the handle but it moves a much bigger load. So we say that it acts as a force multiplier. This is because each force exerts the same moment about the pivot. Moment = force x distance. There is a bigger distance to the effort so the force is smaller. How much smaller depends on the ratio of the distances. Without measuring precisely, I'd estimate that the distance from the pivot to the effort is about 8x the distance from the pivot to the load. So you'd use 8x less force to get the mechanism to move. We call this the mechanical advantage.

 

 

Lower Sixth Estimation Question #6

Calculate the total resistance of all of the current carrying wires between the two pylons shown in the photograph. You need to describe the clue in the photograph that tells us that the very top wire is an Earth wire and can be ignored. You need to state any estimates that you make with reasons.

Roger Bacon in Oxford

Having read about it in the June 2014 edition of Physics World, we went in search of the memorial plaque to Roger Bacon. Thanks to the helpful staff in the Westgate car park, we were able to locate it behind the tree in the top picture on the outside wall of the Westgate shopping centre. Turns out that Roger bacon divides opinion. He was a very early writer on optics and calendar reform. He drew on the work of Islamic scientists. He is credited with being an early advocate of testing claims by doing experiments. It is this latter that seems to have caused most of the arguments in recent years.

Why bubble wrap is so useful

I was very pleased to receive a new mug for my birthday. It came in a bubble wrap parcel. That's because bubble wrap is like a crumple zone. The trapped air in the bubbles crumples up when the parcel is dropped. The crumpling process takes time which means that the change in momentum lasts longer. So the rate of change of momentum is less so the force that would break or scratch my lovely mug is reduced. But that doesn't cover the ideas that Year 10 have been asked to do for their homework. So for the record: If I decided to keep the bubble wrap around the mug when it had a hot drink in, it would act as effective insulation. Air is a bad conductor because the particles are far apart and are not joined. But air is very good at transferring thermal energy by convection. The particles move further apart when they are heated which means that they become less dense than the surrounding air and can thus float upwards. Now if you trap the air in bubbles, you give the air nowhere to go so convection cannot happen. And the trapped air is a bad conductor so it reduces the rate at which thermal energy can leave.