Overview
This lecture explains gravitational force as a fundamental, non-contact force of attraction between masses, how it operates through gravitational fields, and what factors affect its strength.
What is Gravitational Force?
- Gravitational force is a fundamental force of attraction that acts between any two masses.
- It does not require physical contact between objects (non-contact force).
- Gravitational forces are always attractive, never repulsive.
- All objects with mass, no matter how small, exert gravitational forces on each other.
Gravitational Fields and Action at a Distance
- Gravity acts through a gravitational field produced by each mass.
- A gravitational field exists in the space around a mass and exerts force on other masses within it.
- Objects like Earth, Moon, and the Sun produce gravitational fields, attracting other bodies.
Factors Affecting Gravitational Force
- The force depends on the masses of both objects: larger masses create stronger forces.
- Distance between the centers of mass affects gravitational force: as distance increases, gravity becomes weaker.
- For small everyday objects (like two tennis balls), gravity is so weak it's overpowered by other forces, so its effects are not noticeable.
Examples and Applications
- Earth's gravity keeps us on the ground and holds the Moon and satellites in orbit.
- Climbing a mountain does not significantly change gravity's strength due to the Earth's large radius.
- Astronauts in the International Space Station (ISS) still experience significant gravity but appear weightless because they are continuously falling while moving sideways (orbiting).
Key Terms & Definitions
- Gravitational Force — The attractive force between any two masses.
- Non-contact Force — A force that acts without physical contact (e.g., gravity).
- Gravitational Field — The region around a mass where gravitational forces act on other masses.
- Center of Mass — The point in an object or system where its mass is considered to be concentrated.
Action Items / Next Steps
- Read the article “Gravitational forces” in your course materials.
- Think about examples of gravitational force in everyday life and be prepared to discuss in the next class.