17 Gravitational Forces and Fields
Resources
- Video to Watch: Mechanical Universe – Episode 8 – Apple and the Moon
- Extra Help: A-Level Physics Tutor
- Extra Help: Gravity is More Than a Name
- Article to Read: University of Otago (2018) Scientists invent easier, cheaper way to measure gravity
- Article to Read: Carnegie Institution for Science (2018) Outer solar system experts find ‘far out there’ dwarf planet
- Article to Read: NASA’s Goddard Space Flight Center (2018) NASA research reveals Saturn is losing its rings at ‘worst-case-scenario’ rate
Equations Introduced and Used in this Topic:
- [latex]F_g=\dfrac{Gm_1m_2}{d^2}[/latex]
- [latex]a_g \text{ or }g = \dfrac{Gm}{{d}^2}[/latex]
- [latex]\Delta V=-\dfrac{Gm}{d}[/latex]
G = 6.67408(31) × 10−11 Nm2/kg2 (round to needed accuracy)
Where…
- [latex]F_g[/latex] is the Gravitational Force of attraction, measured in newtons (N)
- [latex]G[/latex] is Newton’s Gravitational Constant, currently estimated to be 6.67408(31) × 10−11 Nm2/kg2
- [latex]m_1[/latex] & [latex]m_2[/latex] are the Masses of the two interacting bodies, measured in Kilograms (kg)
- [latex]a_g[/latex] or [latex]g[/latex] is the Gravitational Field Strength of a body, measured in metres/second squared (m/s2) or newtons per Kilogram (N/kg)
- [latex]d[/latex] is the Distance away from the Mass Centre of a Body (gravitational field) or the Distance between Mass Centres of Two Bodies (gravitational fields), measured in metres (m)
- [latex]∆V[/latex] is the potential difference measured in J/kg
| Body | Mass (kg) | Size (radius … m) | Orbit (radius … m)[1] |
|---|---|---|---|
| Sun | 1.9891 × 1030 | 6.980 × 108 | n/a |
| Mercury | 3.302 × 1023 | 2.439 × 106 | 5.791 × 1010 |
| Venus | 4.869 × 1024 | 6.052 × 106 | 1.082 × 1011 |
| Earth | 5.974 × 1024 | 6.371 × 106 | 1.496 × 1011 |
| Mars | 6.419 × 1023 | 3.390 × 106 | 2.279 × 1011 |
| Jupiter | 1.899 × 1027 | 6.991 × 107 | 7.783 × 1011 |
| Saturn | 5.685 × 1026 | 5.832 × 107 | 1.429 × 1012 |
| Uranus | 8.685 × 1025 | 2.536 × 107 | 2.871 × 1012 |
| Neptune | 1.028 × 1026 | 2.462 × 107 | 4.504 × 1012 |
| Moon | 7.349 × 1022 | 1.737 × 106 | 3.844 × 108 |
- Solar Mass (ms) is the mass of the Sun. 1 Solar mass = 1.98855 ± 0.00025 × 1030 kg
- Astronomical Unit (AU) is the distance from Earth to the Sun. 1 AU = 1.49597870700 × 1011 m
17.1 Gravitational Forces
- Article to Read: Physicists set limits on size of neutron stars
- Article to Read: Astronomers Detect Giant Rouge Planet Floating Near Our Solar System
- Article to Read: Boyle, R. (2018) These dusty young stars are changing the rules of planet-building
- Article to Read: The Guardian (2019) Nearby Galaxy set to collide with Milky Way, say scientists
- Article to Read: Where is the universe hiding its missing mass?
- Article to Read: GFZ GeoForschungsZentrum Potsdam (2019) What Earth’s gravity reveals about climate change
- Article to Read: Mass anomaly detected under the moon’s largest crater
Equations Introduced or Used for this Sect