Pearson Edexcel International GCSE (9–1) · PHYSICS · Unit
Astrophysics
156 practice questions
Topics covered
Practice questions
71–78 of 78 · Normal
Question 71
5 marks · Normal
Answer and see the solution →A student is studying two galaxies, Galaxy X and Galaxy Y. She notices that the absorption lines in the spectrum of Galaxy Y are shifted more towards the red end of the spectrum than those of Galaxy X.
(a)[2 marks]Describe what is meant by the term 'red-shift' in the context of light spectra from galaxies.
(b)[2 marks]Explain what the observation about the absorption lines tells us about the relative velocities and distances of Galaxy X and Galaxy Y from Earth.
(c)[1 mark]State how this evidence is related to the theory that the universe began with a Big Bang.
Question 72
5 marks · Normal
Answer and see the solution →Light from a galaxy has a measured wavelength of 660 nm. The same absorption line in the Sun's spectrum has a wavelength of 600 nm.
(a)[1 mark]Calculate the change in wavelength observed for the galaxy's light compared to the Sun's light.
(b)[3 marks]Using the Doppler equation, calculate the speed at which the galaxy is moving away from Earth. Use the speed of light as m/s.
(c)[1 mark]State whether this galaxy is moving towards or away from Earth, and explain your answer.
Question 73
4 marks · Normal
Answer and see the solution →Astronomers use two main types of evidence to support the idea that the universe began with a Big Bang: cosmic microwave background (CMB) radiation and red-shift of galaxies.
(a)[2 marks]Describe what cosmic microwave background (CMB) radiation is.
(b)[2 marks]Explain how CMB radiation and red-shift together act as evidence for the Big Bang theory.
Question 74
4 marks · Normal
Answer and see the solution →The table below shows three planets and their gravitational field strengths:
Planet Gravitational field strength (N/kg) Venus 9 Mars 4 Jupiter 23 A spacecraft has a mass of 500 kg.
(a)[1 mark]State the formula for calculating the weight of an object on a planet.
(b)[2 marks]Calculate the weight of the spacecraft on Mars and Jupiter. Give your answers in newtons (N).
(c)[1 mark]Explain why the spacecraft would weigh so much more on Jupiter than on Mars, using ideas about planets and gravity.
Question 75
6 marks · Normal
Answer and see the solution →A newly launched artificial satellite is put into a circular orbit 2000 km above Earth's surface. Its time period for one complete orbit is 2 hours. The mass of the satellite is 1000 kg. The next night, you observe Jupiter through a telescope and identify several of its natural satellites (moons).
(a)Calculate the orbital speed of the satellite. Give your answer in m/s.
(b)[2 marks]State the SI unit used for mass in astrophysics, and explain whether the mass of the satellite affects its orbital speed.
(c)[1 mark]State one similarity and one difference between the orbits of moons and artificial satellites around Jupiter.
(b)[2 marks]State the SI unit used for mass in astrophysics, and explain whether the mass of the satellite affects its orbital speed.
(c)[1 mark]State one similarity and one difference between the orbits of moons and artificial satellites around Jupiter.
Question 76
5 marks · Normal
Answer and see the solution →The surface gravity on Mars is different from that on Earth. Astronomers also classify stars based on their colour and temperature.
(a)[2 marks]State the unit of gravitational field strength, and then use it to write the weight formula for an object of mass on a planet with gravitational field strength .
(b)[1 mark]If a robot has a mass of 150 kg, calculate its weight on Mars where the gravitational field strength is 4 N/kg.
(c)[2 marks]A scientist observes several stars. One is blue and another is red. Explain which has the higher surface temperature and why, based on the classification of stars by colour.
Question 77
5 marks · Normal
Answer and see the solution →A space probe is launched from Earth to study a distant comet. The probe travels in orbit and astronomers collect data about its motion and the comet's spectrum.
(a)[2 marks]Describe two ways in which the orbit of a comet usually differs from that of a planet in our solar system.
(b)[1 mark]State the reason why an object stays in orbit around another object, such as a probe orbiting a comet.
(c)[2 marks]Scientists observe that the absorption lines in the spectrum of the comet have shifted towards longer wavelengths compared to those from the Sun. What does this tell us about the motion of the comet relative to Earth?
Question 78
4 marks · Normal
Answer and see the solution →A planet named Xon is discovered with a moon that orbits at a radius of 120,000 km and takes 40 days for one complete orbit. The gravitational field strength at the moon's surface is also measured.
(a)[3 marks]Calculate the orbital speed of the moon. Give your answer in km/s.
(b)[1 mark]The moon has a gravitational field strength of 2.5 N/kg. What is the weight of a 50 kg object on the surface of this moon?