MYP Physics Gravity and Gravitational Fields Notes

What Is Gravity And How Does It Act Between Objects With Mass?

1. Gravity is one of the four fundamental interactions in nature.
2. Unlike the strong and weak nuclear interactions, gravity has an unlimited range.
3. Gravitational forces act between any two objects that have mass.
4. The gravitational interaction is always attractive and never repulsive.
5. Although gravity acts between all masses, the force between everyday objects is extremely small and usually unnoticeable.

Gravity as a Force Between Masses

1. Gravity acts between any two objects with mass.
2. The gravitational force between everyday objects is extremely small.
3. The force becomes noticeable when at least one object is very massive.
4. Planets and stars experience strong gravitational attraction.

Everyday Experience of Gravity

1. Gravity pulls objects toward the centre of the Earth.
2. Objects fall to the ground when released because the Earth exerts a gravitational force on them.
3. Humans experience gravity constantly, which is why its effects are often unnoticed.
4. Gravity provides the force that gives objects weight.

Weightlessness and Freefall

1. Astronauts in space often appear weightless.
2. This does not mean gravity is absent.
3. Astronauts experience weightlessness because they are in continuous freefall around the Earth.
4. In freefall, gravity still acts, but there is no supporting force pushing back on the body.

Newton’s Ideas About Gravity

1. Isaac Newton proposed that the same force responsible for an apple falling also governs the motion of the Moon and planets.
2. This idea unified motion on Earth and motion in space under a single explanation.
3. Newton suggested that gravity acts between all objects with mass.
4. He also reasoned that gravity must weaken with distance to explain planetary orbits.

Newton’s Law of Gravitation

1. Newton showed that gravitational force depends on: