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IGCSEPhysicsEdexcelFlashcards8. AstrophysicsMotion in the Universe

Motion in the Universe (Edexcel IGCSE Physics)

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  • List the following objects in order of increasing size:

    Sun, Milky Way, Earth, Universe, Moon

    The objects from smallest to largest size are:

    • Moon (smallest)

    • Earth

    • Sun

    • Milky Way

    • Universe (largest)

  • Define Universe.

    The Universe is a large collection of billions of galaxies.

  • Define galaxy.

    A galaxy is a large collection of billions of stars.

  • What is the difference between a galaxy and the Universe?

    A galaxy is a large collection of stars, whereas the Universe is made up of billions of galaxies.

  • What is the Milky Way?

    The Milky Way is a galaxy containing billions of stars, including our Sun.

  • Which galaxy is our Solar System located in?

    Our Solar System is located in the Milky Way galaxy.

  • True or False?

    The Sun is at the centre of the Milky Way.

    False.

    The Sun is at the centre of the Solar System.

  • Define weight.

    Weight is the force acting on an object due to gravitational attraction.

  • What is the equation for weight?

    The equation for weight is: W space equals space m g

    Where:

    • W = weight, measured in newtons (N)

    • m = mass of the object, measured in kilograms (kg)

    • g = gravitational field strength, measured in newtons per kilogram (N/kg)

  • State the meaning of gravitational field strength.

    Gravitational field strength is the strength of the gravitational pull exerted by an object, such as a planet or moon, on another object on or near its surface.

  • True or False?

    Gravitational field strength is constant at the surface of a given planet.

    True.

    Gravitational field strength is constant at the surface of a given planet, but it decreases with distance above the planet's surface.

  • On which planet in the Solar System would you weigh the heaviest?

    The greater the gravitational field strength of a planet, the greater the measured weight of a person standing on its surface.

    Therefore, you would weigh the heaviest on Jupiter, as this is the largest (most massive) planet.

  • In which direction does the gravitational force of an orbiting body act?

    The gravitational force exerted on an orbiting body acts towards the centre of the larger body it is orbiting.

  • True or False?

    The larger the mass of a planet the greater its gravitational field strength.

    True.

    The larger the mass of a planet the greater its gravitational field strength.

  • True or False?

    All objects in the Solar System orbit the Sun.

    False.

    Planets, comets and asteroids orbit the Sun, whereas satellites (natural and artificial) orbit planets.

  • True or False?

    When planets and satellites orbit larger bodies, they move in approximately circular paths.

    True.

    When a planet orbits the Sun or a satellite orbits a planet, they move in approximately circular paths.

  • Which type of object in the Solar System has the most elongated elliptical orbit?

    Comets have the most elongated elliptical orbits in the Solar System.

  • True or False?

    The Sun is at the centre of an elliptical orbit.

    False.

    When a body moves in a circular orbit, the larger body will be at the centre of the circle.

    When a body moves in an elliptical orbit, the larger body will be at one of the two foci of the ellipse.

    Therefore, the Sun is not at the centre of an elliptical orbit.

  • How does the orbital radius of a planet change with increasing distance from the Sun?

    The orbital radius of a planet increases with increasing distance from the Sun.

  • How does the orbital period of a planet change with increasing distance from the Sun?

    The orbital period of a planet increases with increasing distance from the Sun.

  • How does the orbital speed of a planet change with increasing distance from the Sun?

    The orbital speed of a planet decreases as the distance from the Sun increases.

  • How does the speed of a comet change as it approaches the Sun?

    The speed of a comet changes as it approaches the Sun because it speeds up.

  • Define the term orbital speed.

    Orbital speed is the average speed of an object as it orbits around a larger object.

  • State the equation for calculating orbital speed in terms of distance and time.

    The equation for calculating orbital speed is s p e e d space equals space fraction numerator d i s t a n c e over denominator t i m e end fraction

  • Define the term orbital period.

    Orbital period is the time it takes an object to complete one full orbit around another object.

  • What is the orbital period of the Earth?

    The orbital period of the Earth is 365 days, the time it takes to complete one orbit around the Sun.

  • True or False?

    The orbital radius is measured from the surface of the orbiting body.

    False.

    The orbital radius is always taken from the centre of mass of the orbiting body.

  • What is the distance travelled by an object moving in circular motion in one orbit?

    The distance travelled by an object moving in circular motion is equal to the circumference of the orbit = 2 straight pi r, where r is the radius of the orbit.

  • True or False?

    An object in a circular orbit has a constant orbital radius.

    True.

    An object in a circular orbit has a constant orbital radius.

  • State the equation for orbital speed v, in terms of orbital radius r and time t.

    The equation for orbital speed is v space equals space fraction numerator 2 straight pi r over denominator T end fraction

    Where:

    • v = orbital speed, measured in m/s

    • r = orbital radius, measured in m

    • T = orbital period, measured in s

  • True or False?

    The orbital radius of a satellite in orbit around the Earth is equal to:

    radius of the Earth + height above the Earth's surface

    True.

    The orbital radius of a satellite orbiting the Earth is r space equals space R space plus space h

    Where:

    • r = orbital radius of the satellite, measured in m

    • R = radius of the Earth, measured in m

    • h = height above the Earth's surface, measured in m

Previous:Fission & FusionNext:Stellar Evolution

    1. Topic 1

      Movement & Position

    2. Topic 2

      Forces, Movement & Changing Shape

    3. Topic 3

      Momentum

    4. Topic 4

      Moments

    1. Topic 1

      Current, Potential Difference & Resistance

    2. Topic 2

      Components in Series & Parallel Circuits

    3. Topic 3

      Electrical Power & Mains Electricity

    4. Topic 4

      Static Electricity

    1. Topic 1

      Waves & The Electromagnetic Spectrum

    2. Topic 2

      Reflection & Refraction

    3. Topic 3

      Sound

    1. Topic 1

      Energy Stores & Transfers

    2. Topic 2

      Work, Power & Energy Resources

    1. Topic 1

      Density & Pressure

    2. Topic 2

      Changes of State

    3. Topic 3

      Ideal Gases

    1. Topic 1

      Magnetism & Electromagnetism

    2. Topic 2

      Electromagnetic Induction

    1. Topic 1

      Properties of Radiation

    2. Topic 2

      Radioactivity, Uses & Dangers

    3. Topic 3

      Fission & Fusion

    1. Topic 1

      Motion in the Universe

    2. Topic 2

      Stellar Evolution

    3. Topic 3

      Cosmology