Week 22 Friday Science

In science we talked about gravity, the sun, stars, days and the four seasons. Gravity is a force that attracts all masses, gravity gives you weight not mass, mass never changes and is just how much ‘stuff’ is in an object, weight is a force measured in newtons and changes due to the pull of gravity, Here is the important formula: weight = mass x gravitational field strength  ( which is 10 N on earth ).

The sun is the centre of our solar system

  1. a planet is something which orbits around a star
  2. the Sun is a star, the Earth is one of eight planets which orbit the sun
  3. the Sun is really huge and has a big mass, so it’s gravity is really strong, the pull from the Sun’s gravity is what keeps all the planets in their orbits
  4. the planets all move in elliptical orbits
  5. planets don’t give out light but the Sun and other stars do
  6. the Sun gives out a massive amount of energy which is transferred by light

A galaxy is a large collection of stars, our galaxy is the Milky Way,  the Universe is made up of billions of galaxies. A light year is a unit of distance for measuring very long distances, 1 light year is 9.5 million million km, which means it takes the light from that star 1 year to get to our planet.

Day and night are due to the steady rotation of the Earth, the seasons are caused by the earth’s tilt.

I have already learned all of this so this was just a bit of revision.

Week 22 Friday Maths

On Friday in maths we talked about locus ( plural loci ). A locus is just 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”, this locus is a circle
  2. the locus of points which are “A fixed distance from a given line”, this locus is an oval shape
  3. the locus of points which are “Equidistant from two given lines”, this locus is actually an angle bisector
  4. the locus of points which are “Equidistant from two given points”, the locus is actually the perpendicular bisector of the line joining the two points

That’s all we did in maths but now were going to start doing all the tests.

 

Week 22 Thursday Maths

This is also two days worth of maths, we did: the four transformations ; Pythagoras’ theorem ; bearings ; trigonometry. Translation: the translation vector, how far it’s moved along the x-axis and how far it’s moved up or down the y-axis ; enlargement: the scale factor and the centre of enlargement or two things you need to know ; rotation: you need to know these things, angle turned, direction turned, centre of rotation ; reflection: you need to know where the mirror line is. Pythagoras’ theorem is this: A squared + B squared =H squared, it can only be used on right-angle triangles, here are the three steps:

  1. square the two numbers that you are given
  2. to find the longest side, add them and to find the shorter side, subtract them.
  3. take the square root and that your answer

There are three key points to a bearing:

  1. a bearing is the direction travelled between two points, given as an angle in degrees
  2. all bearings are measured clockwise from the north line
  3. all bearing should be given as 3 figures ( 045 not 45 or 009 not 9 )

After all that we talked about the method for solving right-angle triangles using SIN, COS, TAN:

  1. label the three sides O, A and H ( opposite, adjacent and hypotenuse )
  2. write down SOH CAH TOA
  3. decide which two sides are involved, O H , A H , O A
  4. turn the one you choose into a formula triangle
  5. cover up the thing you want to find
  6. translate into numbers and work it out
  7. finally check that you answer is sensible

the hypotenuse is the longest side, the opposite is the side opposite the angle being used and the adjacent is the side next to the angle being used. Here are a few things about the angle of depression and elevation:

  1. the angle of depression is the angles downwards from the horizontal
  2. the angle of elevation is the angle upwards from the horizontal
  3. the angle of elevation and depression equal each other

That’s all the maths we’ve done over the past couple of days, I understood most of it , but obviously, there is some stuff that went in one side of my brain and came straight out the other.

 

 

Week 22 Thursday Science

This is two days worth of science in one post so it will be quite long, we did: electrical circuits ; static electricity ; magnets ; electromagnets. Electric current is the flow of charge, it’s a bit like water flowing, potential different pushes the current around.

Resistance is how easily electricity can flow, resistance = potential difference / current, circuit diagrams represent real circuits. Opposite poles attract – like poles repel, attraction: north poles and south poles are attracted to each other, repulsion: when you try to attract two of the same poles, they repel each other. The earth has a magnetic field. A wire with a current in it has a magnetic field round it, you can increase the strength of an electromagnetic by:

  1. more current in the wire
  2. more turns on the solenoid
  3. a core of soft iron inside the solenoid

Electric motors are made using an electromagnet.

Week 22 Tuesday Maths

Today in maths we talked about length, area, volume, similarity, enlargement and the four key features of enlargement. There are three rules for identifying formulas:

  1. length formulae (e.g. perimeter) always have lengths occurring singly
  2. area formulae always have lengths multiplied in pairs
  3. volume formulae always have length multiplied in groups of three

Congruence and similarity, congruent: same size, same shape ; similar: same shape, different size. For shapes to be similar, the angles must be the same. For an enlargement of scale factor n:

  1. the sides are, n times bigger
  2. the areas are n squared times bigger
  3. the volumes are, n cubed times bigger

Here are the four key features:

  1. if the scale factor is bigger than 1 then the shape gets bigger
  2. if the scale factor is smaller 1 then the shape gets smaller
  3. the scale factor also tells you the relative distance of old points and new points from the centre of enlargement
  4. the lengths of the two shapes (big and small) are related to the scale factor by this very important formula triangle which you must learn.

Week 22 Tuesday Science

Today in science we talked about currents, parallel and series circuit. Ammeters measure current, voltmeters measure potential difference (volts), batteries and bulbs have potential difference ratings. Here are 2 different circuits:

  1. series circuits: the current has no choice of route
  2. parallel circuits: the current has a choice of route

We didn’t do much today in science because we did another afternoon of filming.

Week 22 Monday Science

Today in science we talked about sound, hearing, energy and waves. Longitudinal waves have vibrations along the same line, sound travels as a longitudinal pressure wave, sound can be reflected and absorbed, the frequency is the pitch of sound and the speed of sound depends on what it’s passing through, it’s slow in air because there are less particles, the more particles, the faster sound waves travel.

Sound waves make your ear drum vibrate, people and animals have different auditory ranges, for example, humans have a range of 20 Hz to 20’000 Hz, dolphins and bats can hear up to 120’000 Hz. Information can be transferred by pressure waves, sound wave energy is detected by diaphragms in microphones, loudspeakers recreate sound waves. Ultrasound is high frequency sound that we can’t hear, ultrasonic cleaning uses ultrasound and you can also do ultrasound physiotherapy that may be helpful (it’s not).