Tuesday and Thursday Week 23 Video

On Tuesday we filmed some stuff on the trampoline and edited it to make a video. We spent like an hour filming and another hour and a half editing it. We soon realised that it was way to long, about 15 minutes. We managed to get it down to about 7 minutes, but that’s still a bit long.

So on Thursday we filmed some other stuff and made a 30 second trampolining video out of it. After we finished editing it we showed it to Simon, who allowed us to publish it, so we did.

I learned some stuff about filming angles. For example: don’t film facing the sun, your best bet would be to have the sun behind, probably. I also realised that it can take a lot of tries before you get it perfect.

Friday Week 22 Maths

As I said in my science post, today we finished maths (the maths in the book, we still have a load of questions to do). In maths we looked at loci (plural for locus)  and constructions.

A locus is a line that shows all the points that fit in with a given rule.

  1. The locus of points which are a fixed distance from a given point will be a simple circle.
  2. The locus of points which are a fixed distance from a given line will be an oval shape.
  3. The locus of points which are equidistant from 2 given lines will be an angle bisector.
  4. The locus of points which are equidistant from 2 given points will perpendicular bisector.

That was about it in maths. I have never heard of a ‘locus’ before, but I understand what it is now.

Friday Week 22 Science

Today we finished both science and maths. We had already finished the other subjects, as you might have noticed. In science we looked at gravity, the sun and the stars, aswell as day and night and the four seasons.

Gravity is a force that attracts all masses. Gravity gives you weight, but not mass (weight and mass aren’t the same thing).

An object has the same mass whether it’s on Earth, Jupiter, or anywhere else. The weight, however, will change depending on the force of gravity. Weight is measured in newtons, on a spring balance. Mass is measured in kilograms, on a mass balance. So when you say “I way 40 kilos” you’re wrong because 40 kg is your mass, not your weight.

Here is an important formula: Weight (in newtons N) = mass (in kilograms kg) x gravitational field strength (in N/kg).

The Sun is at the centre of our solar system. A planet is something which orbits around a star. E.g the sun is a star, the Earth orbits around it so it’s a planet. The difference between a planet and a star is that stars shine, but planets don’t.

A galaxy is a large collection of stars. The Universe is made up of billions of galaxies. Most of the stars you see at night are in our own galaxy, the Milky Way. There are billions of stars in our galaxy, the Sun is one of them. Other stars include the North Star (or pole star, appears above the north pole) and Proxima Centauri (closest star after the Sun).

A light year is a unit of distance. It is, as you might have guessed, how far light travels in a year. It’s for measuring HUGE distances, like those in space. Proxima Centauri is a bout 4 light years away. That means that you look at it, you’re actually looking at what is what it was 4 years ago. In other words, you’re looking into the past, now that’s cool!

Day and night are due to the steady rotation of the earth. It takes the Earth 24 hours to do a full 360° rotation. That’s what a day is: a a full rotation of the Earth on its axis, which is slightly off set. The seasons are caused by this tilt. The Earth takes 365 1/4 days to orbit around the sun, a year (the extra 1/4 day is sorted out every leap year).

Well, I’m still fascinated by the fact that you can look into the past.

Thursday Week 22 Science

After maths, we did some science. In science we looked at static electricity, magnets, and electromagnets.

Charges can build up when objects are rubbed together. All charged objects have an electric field around them. Magnets are surrounded by fields. Opposite poles attract — like poles repel. North poles and south poles are attracted to each other (bar magnets have north and south poles, if you were wondering). If you try to bring 2 of the same magnetic pole together, they will repel each other. The earth has a magnetic field.

While bar magnets stay magnetic all the time, electromagnets can be turned on and off. A wire with a current in it has a magnetic field round it. That’s what electromagnets are: magnets made from current-carying wire. You can increase the strength of an electromagnet: You could add more in the wire, Add more turns on the solenoid, or add a core of soft iron inside the solenoid. Electric motors are made using an electromagnet.

I would quite like to make a small electric motor, at some point.

Thursday Week 22 Maths

Today We started off with some maths. In maths we looked at Pythagoras’ theorem, bearings, and trigonometry.

Pythagoras’ theorem is the formula to find the hypotenuse of a right-angled triangle if you know the other 2 lengths. The hypotenuse is the side opposite the right angle and is always the longest of the 3 sides. The basic formula is: A squared  +  B squared  =  H squared. Here are 3 simple steps to do it:

  1. square the 2 sides that you know.
  2. To find the longest side, add the 2 up. To find a shorter side, subtract the 2.
  3. After that, do the square root of both the added or subtracted sides. Then just check that your answer is sensible.

Here are 3 key points about bearings:

  1. A bearing is the direction travelled between 2 points, given as an angle in degrees.
  2. All the bearings are measured clockwise from the northline.
  3. All bearings should be given as 3 figures. E.g. 045° (not 45°), 316°, 007° (not 7°).

The 3 key words: “From”, “northline”, and “clockwise”.

Trigonometry method (using SIN, COS, and TAN to solve right-angle triangles):

  1. Label the 3 sides O, A and H. (Opposite, adjacent, and hypotenuse)
  2. Write down from memory: “SOH CAH TOA”.
  3. Decide which 2 side are involved — O, H  A, H or O, A and select SOH, CAH or TOH accordingly.
  4. Turn the one you use into a formula triangle: SOH: O / Sθ x H   CAH: A / Cθ x H   TOH: O / Tθ x H.
  5. Cover up the thing you want to find with your finger, and write down what’s left.
  6. Translate into numbers and work it out.
  7. Finally, just check that your answer is sensible.

6 details:

  • The hypotenuse is the longest side.
  • The opposite is the side opposite the angle being used (θ).
  • The adjacent is the side next to the angle being used (θ).
  • θ is a Greek letter called “theta”, and is used to represent angles.
  • In the formula triangles, Sθ represents SIN θ, Cθ is COS θ, and Tθ is TAN θ.
  • YOu can only use these formulas on right-angled triangles.

Angles of elevation and depression:

  1. The angle of depression is the angle downwards from the horizontal.
  2. The angle of elevation is the angle upwards from the horizontal.
  3. The angle of elevation and the angle of depression are always equal.

I think that the whole trigonometry thing is a bit complicated, but not too bad.

Wednesday Week 22 Maths

After science, we did some maths. In maths we looked at the 4 transformations.

  1. Translation. You must know the translation vector in order to be able to it (how far it’s moved along the x-axis and how far it’s moved up or down the y-axis).
  2. Enlargement. You need to know the scale factor and the enlargement point. Even you are shrinking a shape it’s still called an enlargement, the scale factor will just be below 0.
  3. Rotation. You need to know the angle turned, the direction (clockwise or anticlockwise), and the centre of rotation.
  4. Reflection. You need to know the mirror line.

I thought that was pretty straight-forward.