Tuesday, 19 June 2018

Mind Mapping DLO

Gravity

hSMRF and READ this text. Then complete the following responses to text.


  • Highlight the main ideas. Summarize these main ideas  in one or two paragraphs.
  • Gravity is a force that attracts all objects towards each other. Gravitational attraction is
  • greater for more massive objects. Gravity decreases as distance between the objects increases.
  • Every object in the Universe is being attracted towards every other object by the force of gravity.
  • This means that there is nowhere you can go in the Universe where gravity is not acting. Isaac
  • Newton was the first to come up with the idea that all objects are attracted towards each other by
  • gravity. To stay in orbit a satellite needs to be horizontal to the Earth and have enough speed to
  • stay in orbit. At higher altitudes, satellites do not need to be travelling as fast to stay in orbit
  • . Astronauts in the ISS seem weightless because the ISS and the astronauts are falling at the
  • same rate as they orbit around the Earth
  • When does gravity decrease?
  • Gravity decreases as distance between the objects increases.


  • When does the force of gravity become noticeable?


  • Gravity disappears when you are above the atmosphere. True or False?


  • According to the text, how long does it take the International Space Station
  • (ISS) to orbit Earth
  • Who first stated that all objects are attracted towards each other by gravity?


  • Find six words in the text that have a suffix.


Gravity

Gravity is a force that attracts all objects towards each other. People are attracted towards

the Earth and the Earth towards people, the Moon and the Earth are attracted towards each

other, and the Sun and the Earth are attracted towards each other. All of these attractions

are caused by gravity. Gravitational attraction is greater for more massive objects. Gravity

decreases as distance between the objects increases.

Gravity attracts all things towards each other

Every object in the Universe is being attracted towards every other object by the force of gravity.
This means that there is nowhere you can go in the Universe where gravity is not acting. Example
of gravity in action:

  • Gravity holds the atmosphere in place around the Earth.
  • Gravity keeps people on the Earth’s surface.
  • Gravity keeps the International Space Station in orbit around the Earth.
  • Gravity keeps the Moon orbiting around the Earth.
  • Gravity keeps the Earth orbiting around the Sun.
Isaac Newton was the first to come up with the idea that all objects are attracted towards
each other by gravity. Even people are attracted towards each other by gravity, but this force
is so small that it is not noticeable. Gravity only becomes noticeable if one (or both) of the objects
has a lot of mass, such as the Earth.

There is gravity in space



Earth-Moon system and gravity
Any two masses are attracted towards each other by gravity.
This force of gravity causes the Moon to change direction to make it orbit around the Earth.


Gravity doesn’t disappear just because you are above the atmosphere.
Even if an object is high above the Earth’s atmosphere, there will still be
a strong force of gravity pulling it towards the centre of the Earth. At an altitude of 30 km,
you would be above 99% of the Earth’s atmosphere. At 100 km, you would officially be in
space, yet the weight force of gravity would still be nearly the same. You and the Earth would
still be pulled together.
Isaac Newton worked out that, if the distance from the centre of the Earth doubles,
gravity becomes a quarter as much as it was on the surface. A satellite with a mass
of 1000 kg has a weight force of 9800 N at the Earth’s surface. The radius of the Earth is about
6366 km, so at 6366 km above the Earth’s surface, the distance from the centre of the Earth will
have doubled. The weight force pulling it towards the centre of the Earth will now only be a quarter as
much but will still be 2450 N.


So why doesn’t a 1000 kg satellite just fall back to Earth?


Sideways speed keeps satellites in orbit.

As a satellite moves around the Earth in a circular orbit, the direction of the force of gravity is
always towards the centre of the Earth.
At an altitude of 100 km, you would be so high that you would see black sky and stars if you looked
upwards. If you took a satellite to this height and released it, it would still fall towards the
Earth because the force of gravity is nearly the same as it is at the Earth’s surface.


However, if the satellite is given speed in any direction horizontal to the surface of the Earth,
it will travel further before it hits the Earth. If it is given enough speed, it will travel so far that, as it curves
towards the Earth, it will miss the Earth altogether. At just the right speed, it will move around the Earth
in a circular motion. This type of motion and the path that a satellite moves in is called an orbit.


Close to the Earth at an altitude of 100 km, a satellite needs to be moving at 8 kilometres per second
(28 000 km/h) to stay in orbit. At higher altitudes, satellites do not need to be travelling as fast. T
elevision communication satellites are at a higher altitude of 36 000 km and only need to travel at 3 km/s
(11,000 km/h).


The Moon is 360,000 km from the Earth and only needs to be travelling at 1 km/s to stay in orbit
around the Earth.


If there is gravity in space, why do astronauts appear weightless?
Astronauts appear to be weightless for the same reason that a person on a trampoline feels
weightless when in the air. There is still the same amount of gravity acting, but there is no floor
pushing upwards on the astronaut, so the weight force cannot be felt.


If a person was in an elevator and the cables broke and the brakes failed
(we are assured this cannot happen), the person and the elevator would fall towards the Earth at
the same rate.
The floor would not be holding the person upwards, so the person could enjoy the sensation of
weightlessness (for a brief while).


This is the same for astronauts high above the atmosphere on the International Space Station
(ISS) at an altitude of about 400 km. Gravity is still strong, but the astronaut and the ISS fall
towards the ground at the same rate.
They are also both travelling horizontally at 28,000 km/h. As they fall towards the ground
, they travel so fast horizontally
that they miss the Earth altogether and orbit the Earth once every 90 minutes.

Nature of science Science ideas change over time. Isaac Newton’s gravity-based world view has since been superseded by Albert Einstein’s ideas that all masses distort space and time. This highlights the fact that science is not a fixed body of knowledge. Although Einstein’s theory is widely accepted, Newton’s law of universal gravitation is still used for practical situations such as satellite motion.




Space Inquiry

Friday, 6 April 2018

Common Wealth Games Time Line

Today in class we were learning how to use a Time line. In a time line you have to click the line to get a box. Also for the time line we did it around Common Wealth Games from 1930 to 2018.

Wednesday, 4 April 2018

Thursday, 22 March 2018

Treat Of Waitangi




Create - Literacy. WALT: I am learning to focus on meaning as a clue to work out the meanings of complex, irregular, academic, content specific and ambiguous vocabulary.
Learning Challenge: Undertake and complete the scavenger hunt for Te Tiriti o Waitangi and your guided reading work on Te Tiriti o Waitangi.

Show how you would

  • Decode a new word.

  • Identify which meaning is correct when working with an ambiguous word or phrase.   

  • Locate information within a text.

  • Ask and/or respond accurately to questions about a guided reading text.

  • Collaborate with a buddy to create a modern treaty for all New Zealanders to sign up to in 2018.  What do you think are the most important ideas to agree to? How will you make the document fair to all? How will you include diversity and acceptance of others?
We will have met the success criteria when we
  • Can work out the meaning of new vocabulary.

  • Can independently locate information within a text.

  • Can show that we understand the intent of the text we are reading.