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Space physics: GCSE Combined Science Physics practice questions

Foundation and Higher · Grade 6

A second set of questions on space physics. They are different from the ones on the topic page. Try each, then open the answer and compare your working.

More questions

Question 1 Hard

Satellite X orbits closer to the Earth than satellite Y. State which has the greater orbital speed and explain why.

Show answer

Answer: X is faster, because gravity is stronger closer to the Earth, so it needs a greater speed to stay in orbit.

  1. Gravity is stronger closer to the Earth.
  2. A stronger pull needs a greater speed to stay in orbit, so X is faster.

Question 2 Hard

Explain how the red-shift of light from distant galaxies is evidence for the Big Bang.

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Answer: Distant galaxies are red-shifted, so they are moving away, and the further they are the faster they move. The universe is expanding from a small, hot start.

  1. Distant galaxies are red-shifted, so they are moving away.
  2. The further the galaxy, the faster it moves away, so the universe is expanding from a small, hot start.

Question 3 Hard

A star has a mass much greater than the Sun. State what it may become after a supernova.

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Answer: a neutron star or a black hole

  1. A very massive star ends in a supernova.
  2. The core that is left is a neutron star or a black hole.

Question 4 Hard

Galaxy A is further from us than galaxy B. Compare their red-shifts and state what this shows.

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Answer: A has the greater red-shift, so it is moving away faster than B.

  1. Further galaxies have a larger red-shift.
  2. So A is moving away faster than B.

Quick checks

Short questions with options. Choose one before you open the answer.

Check 1

What is a satellite, and is the Moon natural or artificial?

  1. An object that orbits a bigger one. The Moon is natural.
  2. A star that gives out light. The Moon is artificial.
  3. A cloud of gas and dust. The Moon is a planet.
Show answer

An object that orbits a bigger one. The Moon is natural. Any object in orbit round a bigger one is a satellite. Moons are natural and man-made ones are artificial.

Check 2

Which force keeps the planets in orbit around the Sun?

  1. friction
  2. gravity
  3. magnetism
Show answer

gravity Gravity pulls each planet towards the Sun and keeps it curving round.

Check 3

What is the unit of weight?

  1. the kilogram, kg
  2. the joule, J
  3. the newton, N
Show answer

the newton, N Weight is a force, so it is measured in newtons.

Check 4

What is the equation for weight, in words and symbols?

  1. weight = mass × g
  2. weight = mass ÷ g
  3. weight = mass + g
Show answer

weight = mass × g Each kilogram weighs g newtons, so multiply the mass by g.

Check 5

Take g = 10 N/kg. What is the weight of a 5 kg bag on the Earth?

  1. 0.5 N
  2. 50 N
  3. 15 N
Show answer

50 N W = m × g = 5 × 10 = 50 N.

Check 6

An astronaut has a mass of 70 kg on the Earth. What is her mass on the Moon?

  1. 112 kg
  2. 7 kg
  3. 70 kg
Show answer

70 kg Mass stays the same everywhere. Only the weight changes.

Check 7

Why does the same astronaut weigh less on the Moon than on the Earth?

  1. The Moon has a smaller g.
  2. She loses mass in space.
  3. There is no gravity on the Moon.
Show answer

The Moon has a smaller g. Weight = mass × g, and g on the Moon is about 1.6 N/kg compared with 10 N/kg on the Earth.

Check 8

What is the difference between speed and velocity?

  1. Speed has a direction. Velocity does not.
  2. Velocity has a direction. Speed does not.
  3. They mean exactly the same thing.
Show answer

Velocity has a direction. Speed does not. Velocity = speed plus a direction.

Check 9

Why does a satellite in a circular orbit accelerate when its speed is constant?

  1. Its speed keeps changing.
  2. Rocket engines push it all the time.
  3. Its direction changes, so its velocity changes.
Show answer

Its direction changes, so its velocity changes. A change in velocity is acceleration, and direction is part of velocity.

Check 10

Which way does the resultant force on an orbiting satellite point?

  1. towards the centre of the orbit
  2. straight ahead, along its path
  3. away from the Earth
Show answer

towards the centre of the orbit Gravity pulls the satellite inwards all the time, so the resultant force points to the centre.

Check 11

A student says, "No force acts on a satellite in orbit." What is wrong?

  1. Nothing is wrong, because there are no forces in space.
  2. Gravity acts on it all the time.
  3. A rocket force acts on it.
Show answer

Gravity acts on it all the time. Gravity is the resultant force, pointing to the centre of the orbit.

Check 12

Which orbits faster: a satellite close to the Earth or one far away?

  1. the far one, because it has further to go
  2. both orbit at the same speed
  3. the close one
Show answer

the close one A stronger pull needs a higher speed to stay in a steady orbit.

Check 13

Higher tier: if the orbital speed of a satellite changes, what happens to its orbit radius?

  1. The radius changes too.
  2. Nothing, because speed does not affect the radius.
  3. The satellite just stops.
Show answer

The radius changes too. Speed and orbit radius are linked for any steady orbit.

Check 14

What equation links speed, distance and time?

  1. speed = distance × time
  2. speed = distance ÷ time
  3. speed = time ÷ distance
Show answer

speed = distance ÷ time Speed is how much distance is covered in each unit of time.

Check 15

A probe travels 600 km in 2 hours. What is its average speed?

  1. 1200 km/h
  2. 598 km/h
  3. 300 km/h
Show answer

300 km/h speed = distance ÷ time = 600 ÷ 2 = 300 km/h.

Check 16

What is a nebula?

  1. a huge cloud of dust and gas
  2. a star at the end of its life
  3. a rocky object that orbits the Sun
Show answer

a huge cloud of dust and gas Gravity pulls a nebula together to make a new star.

Check 17

What is nuclear fusion?

  1. a large nucleus splitting into two
  2. small nuclei joining into a bigger one
  3. a fuel burning in oxygen
Show answer

small nuclei joining into a bigger one Fusion of hydrogen into helium is the energy source of a main sequence star.

Check 18

Why is a main sequence star stable?

  1. It is a solid ball.
  2. Fusion has stopped.
  3. Pressure out balances gravity in.
Show answer

Pressure out balances gravity in. The balance of forces keeps the star the same size for billions of years.

Check 19

What does a star like the Sun become after the red giant stage?

  1. a white dwarf
  2. a black hole
  3. a supernova
Show answer

a white dwarf A Sun-like star sheds its outer layers and the core becomes a white dwarf.

Check 20

What can a very massive star leave behind after a supernova?

  1. a white dwarf and a planet
  2. a neutron star or a black hole
  3. a new red giant
Show answer

a neutron star or a black hole The core left behind is so dense that it forms a neutron star or a black hole.

Check 21

What happens to the wavelength of light from a galaxy moving away from us?

  1. It gets shorter.
  2. It does not change.
  3. It gets longer.
Show answer

It gets longer. Stretched waves have a longer wavelength, which moves light towards the red end.

Check 22

Galaxy A is twice as far away as galaxy B. How do their red-shifts compare?

  1. A has the bigger red-shift.
  2. B has the bigger red-shift.
  3. They have the same red-shift.
Show answer

A has the bigger red-shift. Further galaxies move away faster, so their red-shift is bigger.

Check 23

What is the cosmic microwave background, and which model does it support?

  1. Light from galaxies moving towards us. It supports the Steady State model.
  2. Leftover radiation from the hot early universe. It supports the Big Bang.
  3. Radio signals from artificial satellites. It supports no model.
Show answer

Leftover radiation from the hot early universe. It supports the Big Bang. The Big Bang predicts this glow, but the Steady State model cannot explain it.

Check 24

What is a galaxy, and what is our own galaxy called?

  1. A single star and its planets. Ours is the Solar system.
  2. A huge group of stars. Ours is the Milky Way.
  3. A cloud of gas where stars form. Ours is the Andromeda nebula.
Show answer

A huge group of stars. Ours is the Milky Way. The Sun is one of billions of stars in the Milky Way.

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