The universal attractive force between any two objects with mass, decreasing with the square of distance. Governs planetary motion, ocean tides, and keeps us on Earth's surface.
Definition
The universal attractive force between any two objects with mass, decreasing with the square of distance.
💡 Intuition
Everything pulls on everything else—but only huge things (like Earth) pull noticeably.
🎯 Core Idea
Gravity acts between all masses everywhere — it never turns off, only weakens with distance.
Example
Formula
Notation
G is the universal gravitational constant (6.674 \times 10^{-11} N m^2 kg^{-2}), m_1 and m_2 are the two masses in kilograms, and r is the centre-to-centre distance in metres.
🌟 Why It Matters
Governs planetary motion, ocean tides, and keeps us on Earth's surface.
💭 Hint When Stuck
When you see a gravity problem, identify the two masses and the distance between their centres. First, substitute m_1, m_2, and r into F = Gm_1 m_2 / r^2. Then compute the numerator and denominator separately before dividing. Finally, check your answer's units are in newtons.
Formal View
Related Concepts
Compare With Similar Concepts
🚧 Common Stuck Point
Gravity never 'turns off' in space—astronauts float because they're falling around Earth.
⚠️ Common Mistakes
- Using the distance between surfaces instead of the distance between the centres of mass of the two objects.
- Forgetting to square the distance r in the denominator, which drastically changes the result.
- Confusing g (gravitational field strength, ~9.8 m/s²) with G (the universal gravitational constant, 6.67 × 10⁻¹¹ N m²/kg²).
Common Mistakes Guides
Go Deeper
Frequently Asked Questions
What is Gravity in Physics?
The universal attractive force between any two objects with mass, decreasing with the square of distance.
What is the Gravity formula?
When do you use Gravity?
When you see a gravity problem, identify the two masses and the distance between their centres. First, substitute m_1, m_2, and r into F = Gm_1 m_2 / r^2. Then compute the numerator and denominator separately before dividing. Finally, check your answer's units are in newtons.
Next Steps
Cross-Subject Connections
How Gravity Connects to Other Ideas
To understand gravity, you should first be comfortable with force and mass. Once you have a solid grasp of gravity, you can move on to weight, orbital motion and gravitational field.
🧪 Interactive Playground
Drag to explore. Click to commit changes.