MULTI-PATHS DESKTOP PRESENTATION

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Astrophysics

• A star is a body which emits energy powered by nuclear fusion.
• A planet orbits a star
• A moon orbits a planet

1. The universe is a large collection of billions of galaxies
2. A galaxy is a large collection of billions of stars
3. Our solar system is in the Milky way galaxy

Motion in the universe

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The strength of the gravitational field strength for a planet depends on its radius and density. A larger field is produced by a planet with a larger density and larger radius.

Every planet, moon or star has a gravitational field strength,g, at its surface. On earth its about 10 N/kg. This means that the mass of 1kg is pulled down with a force of 10N. This force is the object's weight.

Gravitational field strength

An orbit is... The curved path of one celestrial object or spacecraft around another celestrial object. (This could be the earth orbitting the sun) or (the moon orbiting the earth)

Use: "https://www.youtube.com/watch?v=cTJLYfEHluA" for explanation how gravitational force causes orbits in space.

Gravity in Space

While gravity acts close to the Earth to pull things to the ground, it is also a force that stretches an enormous distance out into space. Gravity acts on all stars, planets and moons. - Gravity causes planets and comets to orbit the Sun - Gravity causes the Moon and artificial satelittes to orbit the earth -Gravity causes the stars to orbit the centre of their galaxies

This image shows the pull of gravity from the earty, which keeps the moon in orbit. The moon has an 'instantaneous velocity of 1023 m/s, the pull of gravity from the earth deflects its motion. When it has moved position the force of gravity does not make the moon travel any faster, but the force changes the direction of motion. (because the direction of the object is changing its velocity is also chnaging which means its accelearting.)

Gravitational Force

To avoid getting sucked into the earth the moon would have to start travelling at a much faster speed, so its instananeous velocity would increase allowing it to have a stable orbit.

Use: "https:/www.youtube.com/watch?v=FMsi89W9mvk For better understanding of orbital radius

Planets and moons move in eliptical orbits. However, many of the orbits for the planets and moons in our solar system are nearly circular. The speed of orbit of a moon, planet or staelitte can then be related to the radius and time of orbit using the following equation:

• If its speed is too great, it disappears into outer space
• If its speed is too slow, it falls into Earth
• When the satelitte moves at the right speed, it stays in a steady circular orbit.

Speed of orbit is very important. Take a Satlitte as an example

Speed of orbit

If a planet is close to the sun, the pull of gravity from thesun is strong. This causes the speed of the orbit to be high. For a planet further away, the Sun's gravity pulls less strongly and the planet moves more slowly. We can use this data to calcuate the orbital speeds for Earth and mercury: the Earth orbits the sun with an orbital radius of 150 million kilometres, and mercury orbits the sun with an orbital radius of 58 million kilometres.

Orbits near and far

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resources

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• Genially. (2014, June 10). Genially. Retrieved June 15, 2020, from https://www.genial.ly
• Genially. (2014, June 10). Genially. Retrieved June 15, 2020, from https://www.genial.ly
• Genially. (2014, June 10). Genially. Retrieved June 15, 2020, from https://www.genial.ly
• Genially. (2014, June 10). Genially. Retrieved June 15, 2020, from https://www.genial.ly
• Genially. (2014, June 10). Genially. Retrieved June 15, 2020, from https://www.genial.ly

Lorem ipsum dolor sit amet, consectetuer adipiscing elit.

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