Wave amplitude in Hartlepool harbour

 

I was able to use binoculars to watch the swell against the depth marker on the harbour wall. It was in a mean position of 5.40m and max was 5.60m. The minimum was on a part of the scale that had been obliterated. The amplitude seems to be 20cm.

Keeping the sandwich hot

 

Once upon a time before lockdown we went to see the snowdrops at the Bake Off garden. We had a lovely lunch with wonderful cakes. They served the hot sandwiches in foil lined bags. The shiny surface should reflect infra-red radiation from the sandwich back inside the bag so making it harder for the sandwich to lose thermal energy. I should have looked harder to see if the paper outer was attached to the foil. A slight air gap would have increased the insulating properties. Paper doesn't conduct as well as metal so it wouldn't be as hot to hold. 

Full spectrum at Seaton Carew

 

These beach huts at Seaton Carew cover the visible spectrum very well. We physicists just get obsessed with the colours having the correct order of wavelength ... !

Thrust from a jet engine

 

This engine is on display at Watchtree, the result of a terrible crash some years ago. The data says a maximum thrust of 40kN. https://en.wikipedia.org/wiki/Panavia_Tornado says that the maximum mass of the loaded plane is about 20,000 kg. By  the Newton's 2nd Law equation F=ma, this gives a maximum acceleration of 2m/s/s. That doesn't sound very much and also ignores any counter forces like friction and drag. Following the references to source gets some very different data http://www.aerospaceweb.org/aircraft/bomber/tornado_ids/ It turns out that the plane had 2 engines and that the maximum thrust was 149.5kN. It doesn't say if that is total or for one engine, but let's take it as total. With no friction or drag, acceleration would be about 7.5m/s/s which is getting close to g.

Sandford Hydro data

 

https://www.lowcarbonhub.org/p/projects/sandford-hydro/ says that the hydro generates 1.6GWh every year and runs at 440kW. 1.6 x 10^9 divided by 365.25 divided by 24 = 182kW. This must be the average power with 440kW the peak, I suppose. 1.6 x 10^9 divided by 450 = 3500kWh roughly or a household electricity bill of around £400 a year.

Wetsuits

 

I hadn't worn a wetsuit before but was offered use of one for a dip in the sea. I have often wondered about why a swimming pool at 18 degrees feels much colder than the air at 18 degrees. I think that this is because the particles are closer in the water so it can conduct heat better. The wetsuit seems to work by trapping a layer of water and heating only that. As long as that remains next to the skin and is not replaced by cold water, thermal equilibrium is reached between the body and that layer of water so the body doesn't cool down further. The outer rubber layer means that the trapped layer of water loses heat slowly to the surrounding sea. It is well explained in detail at https://www.explainthatstuff.com/howwetsuitswork.html

Biggest person sits here

 

I was interested in this sign at the fair in Hunstanton. As the ride spins fast, the any object with inertial mass will tend to go in a straight line and will need a centripetal resultant force to pull it round in a circle. The heavier the person, the more force needed. Centripetal force = mass x radius x (angular velocity)^2. All objects wil have the same angular velocity. Putting the biggest mass on the biggest radius will mean a bigger centripetal force required. But more mass further out increases the moment of inertia of the ride which would mean that it will tend to go slower. We wondered whether the practical reason was that the heavier person would have more of a tendency to go straight on and would thus be more likely to crush the person outside them if sat on the inside seat.