## dynamics & space revision questions

Here are the revision questions for dynamics and space.  They are taken from old standard grade and intermedite 2 past papers.  I have adjusted the marks to fit national 5.

## nat5 revision

Use the attached file to help with revision for your test on Monday.  Start at the beginning of the booklet and read up to the end of page 41.

Thanks to Mr Noble for sharing his notes. 🙂

## nat5 – work, power and potential energy

We’ve been looking at work and the rate of change of energy.  This handout will help you to revise the key points and introduces gravitational potential energy.

## Newton’s third law of motion

Today we examined the importance of Newton’s 3rd law of motion. In our discussions, different explanations for the motion of jets and rockets were proposed and considered. The front runners were;

1. at launch, the ground pushes back against a rocket
2. during flight, air pushes back against a plane

Unfortunately, the lack of ground and air (or any other gas) meant that neither of these models were able to explain the propulsion of an object in space. It was at this point we remembered Newton’s 3rd law of motion (or here with non-rocket examples).

You’ve got to be careful with Newton’s 3rd law of motion, it’s easy to get confused. Bonus question: What’s wrong with this explanation?

I found a photograph that provides a stunning visualisation of Newton’s 3rd law in action during the launch of a DeltaIV rocket. You can read the details of setting up for this photo here.

image courtesy of Ben Cooper, Launchphotography.com

The photo was taken at very short range (about 30m) from the launch site and clearly shows hot gases being forced out of the exhaust at high speed. When a rocket forces out gas, the expelled gas pushes back on the exhaust with an equal force. Since the exhaust is part of the rocket’s structure, the entire rocket is propelled in the opposite direction to the gas.

It is this pushing back on the exhaust that provides thrust for a rocket. It doesn’t matter if the rocket is on the launch pad, in mid air or outer space. As long as it can push gas out of the exhaust, it will be able to propel itself forwards using Newton’s 3rd law of motion.

We don’t normally get a clear view of the hot gases being forced out of a rocket in launch photographs. A lot of the smoke seen in images like the one shown below is actually steam.

NASA/courtesy of nasaimages.org

There are two main sources of steam during launch. The most obvious is the burning of fuels but NASA also soaks launch platforms with water just before and after launch so that the massive sound waves don’t damage the vehicle being launched. There is a wikipedia article on the use of water during space shuttle launches.

## Nat5 dynamics & space questions

Some of you asked for revision questions ahead of the unit assessment.  Down load these problems from older past papers.  I will add a secoond post with the answers shortly.

## temperature, colour and line spectra

We’ve been looking at how the temperature of an object can affect it’s appearance.  The attached handout recaps on our work in class and provides some examples of line spectra.

## changing state – latent heat of fusion/vaporisation

Before the holidays, we performed a set of experiments to determine the latent heat of fusion and latent heat of vaporisation of water.  Next week, we’ll review that work and think about possible reasons why our results were not closer to the “book” values.

The attached pdf provides a summary of the topic.

## 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.

If you want to download a copy of the video to watch later, use the download link below.  Please be patient, the file is about 660MB in size.