ConceptConceptDocsDocuments

Edexcel A-Level Physics Astrophysics and Cosmology

Practise Edexcel A-Level Physics astrophysics and cosmology through gravitational fields, stellar radiation laws, HR diagrams, parallax, redshift and Hubble’s law.

Syllabus
Pearson Edexcel International Advanced Subsidiary/Advanced Level
Course
Physics XPH11/YPH11
Level
A2

Exam points

  • calculate gravitational field strength, potential energy or orbital quantities in radial fields
  • use Stefan-Boltzmann, Wien’s law and intensity equations to compare stellar properties
  • interpret HR diagrams, parallax, Doppler shift and Hubble’s law for stars and galaxies

Covered syllabus points

5.6.154 - Gravitational fields5.6.155 - Gravitational field strength5.6.156 - Newton’s law of universal gravitation5.6.157 - Gravitational field due to a point mass5.6.158 - Gravitational potential in a radial field5.6.159 - Electric and gravitational fields comparison5.6.160 - Orbital motion5.6.161 - Black body radiation curves5.6.162 - Stefan-Boltzmann law5.6.163 - Wien’s law5.6.164 - Radiation intensity from luminosity and distance5.6.165 - Distance by trigonometric parallax5.6.166 - Distance by standard candles5.6.167 - Hertzsprung-Russell diagram5.6.168 - Hertzsprung-Russell diagram and stellar life cycles5.6.169 - Doppler effect5.6.170 - Redshift and Hubble’s law5.6.171 - Age and fate of the universe

5.6 - Astrophysics and Cosmology question 1

[Maximum number: 9]

The dwarf planet Ceres is the largest object in the asteroid belt.
Ceres has a mass of 9.38×1020 kg9.38 \times 10^{20} \mathrm{~kg}. Ceres has a circular orbit of radius 4.14×1011 m4.14 \times 10^{11} \mathrm{~m} around the Sun.

Question (a)

(a)

Show that the gravitational force exerted on Ceres by the Sun is about 7×1017 N7 \times 10^{17} \mathrm{~N}.

 mass of Sun =1.99×1030 kg\text { mass of Sun }=1.99 \times 10^{30} \mathrm{~kg}
[ 2 ]

Question (b)

(b)

Determine the time T, in years, for Ceres to make one complete orbit about the Sun.

1 year =3.15×107 s=3.15 \times 10^{7} \mathrm{~s}

T= years \begin{aligned} & T= \\ & \text { years } \end{aligned}
[ 4 ]

Question (c)

(c)

Mercury is the smallest planet in our solar system. The gravitational field strength gmg_{\mathrm{m}} at the surface of Mercury is 3.7Nkg−13.7 \mathrm{Nkg}^{-1}.

It is claimed that the gravitational field strength at the surface of Ceres is less than 5% of gmg_{\mathrm{m}}.

Evaluate whether this claim is accurate.
radius of Ceres =470 km=470 \mathrm{~km}

[ 3 ]

5.6 - Astrophysics and Cosmology question 2

[Maximum number: 11]

Weather satellites may be in an equatorial orbit or a polar orbit, as shown.

Question (a)

(a)

A weather satellite in a polar orbit circles the Earth at a height of 8.50 × 10^5 m above the surface of the Earth.

[ 4 ]

Question (i)

(i)

Show that the gravitational potential at this height is about −5.5 × 10^7 J kg^-1.
mass of Earth = 5.98 × 10^24 kg
radius of Earth = 6360 km

[ 2 ]

Question (ii)

(ii)

Hence calculate the increase in gravitational potential energy when the satellite is placed in orbit.
satellite mass = 4990 kg
gravitational potential at the Earth’s surface = −6.27 × 10^7 J kg^-1

Increase in gravitational potential energy =

[ 2 ]

Question (b)

(b)

It is claimed that a satellite in orbit at a height of 8.50×105 m8.50 \times 10^{5} \mathrm{~m} would make 15 orbits of the Earth every 24 hours.

Assess the validity of this claim.

[ 5 ]

Question (c)

(c)

It is suggested that the satellite could be placed in an equatorial orbit at a radius of 42200 km . With this radius the satellite would have an orbital period equal to 24 hours.

Give one advantage and one disadvantage of placing a weather satellite in a polar orbit rather than in the suggested equatorial orbit.

[ 2 ]
All question bank results loaded