## national 5 – satellites

We’ve started looking at telescopes and this BBC programme from 2 years ago featured the replacement for Hubble, the James Webb Space Telescope.  The presenter, Maggie Aderin Pocock now hosts The Sky at Night on BBC4.

Please take some time to watch both parts of the film.  Maggie covers the basic idea of satellites, how we achieve geostationary orbit, looks at examples of Earth observation and the manufacture of the James Webb’s massive 6.5m mirror.  In part 1, around 17 minutes in, you’ll see satellite footage over the Highlands, can’t quite see Thurso though.

## S4: work done, potential and kinetic energy

We finished the transport section with a look at Work, Potential & Kinetic energy.  Those of you aiming for Credit need to carry out calculations involving kinetic energy using

$E_k = \displaystyle {1 \over 2}mv^2$

Here is a video about work, potential energy & kinetic energy from Bozeman Science

Most of the calculations will be based on the principle of conservation of energy.  Dr. Altman has an excellent series of videos examining conservation of energy  examples from Roadrunner cartoons.

I have attached a pdf handout with worked examples on potential energy, work and kinetic energy.  If you want some more revision materials, try here.

## S3 homework solutions

Here are the solutions to the HW exercise I set before Christmas.  I am pleased to see so many of you showing full working.

## re-entering the earth’s atmosphere

In space there is no air resistance to oppose motion, so the Space Shuttle orbiter can travel at very high speeds, up to 17,321 mph!  At these speeds, the orbiter experiences enormous air resistance as it descends into the Earth’s atmosphere at the end of its mission.

This air resistance is just like any other form of friction – it converts kinetic energy into heat energy.  The effect of this heat energy is demonstrated in this video clip taken by a Canadian police car camera.  It shows a meteor burning up in the atmosphere above Edmonton.

Thankfully most meteors do burn up in the atmosphere, although the dinosaurs were not so lucky.

The high temperatures created during re-entry ionise the gas around the orbiter and this is often seen as a bright light in NASA cockpit videos, such as the one shown below.

To protect the vehicle and its crew from these high temperatures, the underside of the orbiter is covered by a layer of heat resistant tiles called the thermal protection system.  This NASA clip explains how the tiles are constructed and arranged on the underside of the orbiter.

When Columbia was launched in 2003, something fell against the insulation on the left wing and knocked off some of the tiles.  This hole in the thermal protection system caused Columbia to explode over the US as it re-entered the atmosphere.  There is a wikipedia article about the Columbia disaster.

Video footage of NASA’s Houston control room from the morning of the disaster was included in the BBC Horizon documentary Final Descent – Last Flight of Space Shuttle Columbia.

WARNING: This last film is an excerpt from the Horizon programme and includes genuine cockpit video that was found in the wreckage, with some clips of the crew’s final minutes before they were killed.

There is a good description of the Space Shuttle at How Stuff Works.

## colour, temperature and emission spectra

Today we looked at emission spectra from different light sources; mercury, sodium, cadmium and oxygen discharge tubes, using a handheld spectroscope.

Here is a video that shows you how to make a basic spectroscope at home.  There are lots of guides like this online.  You might prefer to make a larger spectroscope by using a Pringles tub rather than an old toilet roll holder as the main tube.

I have attached the handout on colour and emission of light from different elements below.