Newton's Laws of Motion

Flashcards reviewing Newton's laws, gravity, inertia, and orbital motion.

Gravity

The force of attraction between objects with mass.

Universal Gravitation

Newton's law describing the gravitational force between objects.

Newton's First Law of Motion (Law of Inertia)

An object at rest stays at rest, and an object in motion stays in motion with the same speed and direction unless acted upon by a force.

Inertia

Resistance to change in speed or direction.

Direct Relationship

A relationship where if one variable increases, the other variable also increases.

Orbital Motion

The movement of one object around another due to the combined effects of gravity and inertia.

Vectors

The path an object takes when influenced by both inertia and a force pulling it inward; results from the combination of inertia and gravity.

Matter

The "stuff" that something is made of, consisting of atoms and molecules.

Mass vs. Weight ⚖️

Mass and weight are often confused. For example, the air contains nitrogen molecules, but they have so little mass that gravity barely pulls on them. Conversely, tables and chairs have enough matter to have a substantial mass, and therefore a notable weight, allowing them to stay on the surface.

Space Mission to Mars 🚀

Imagine you are selected for a space mission to Mars.

On Earth, your mass is 102 kilograms (102,000 grams).

On the Moon, your mass remains 102 kilograms.

Your mass, the amount of "stuff" in you, stays the same regardless of location. On Earth, this mass equates to 225 pounds of weight due to Earth's gravity. However, on the Moon, you'd weigh only 37.5 pounds.

The reason for this difference is the Moon's weaker gravitational pull because the Moon is a smaller object. It has one-sixth the gravity of Earth because it is one-sixth the size of Earth.

Location

Mass

Earth

102 kg

Moon

102 kg

Newton's Laws of Motion 📜

Newton's First Law: The Law of Universal Gravitation

"Universal" here means "always the same" or "everywhere," not just "in the universe." Gravity acts everywhere, not just on Earth.

The law of universal gravitation: Every object in the universe attracts every other object.

Everything has gravity—tables, you, Mars, even cards. So, why don't we see everything pulled together? Earth's gravity is much stronger and overwhelms the tiny gravitational forces between smaller objects due to Earth's large size.

The force of gravity depends on:

The mass of the objects

The distance between them

If you go far enough into space, away from Earth's gravity, you can float.

🚀 Gravity and Space

Escape Velocity

When launching a rocket into space, it's crucial to calculate the escape velocity needed to overcome Earth's gravitational pull. Thrust, the force exerted by the rocket's engine, must be sufficient to achieve this velocity.

Gravitational Relationships

The force of gravity is influenced by two key factors:

Mass: Gravity has a direct relationship with mass. As mass increases, gravity increases, and vice versa. This relationship can be represented as $A \propto B$, where A and B both go up or down together.

Distance

Gravity has an inverse relationship with this. As distance it increases, gravitational force decreases. This can be represented as A alpha B, meaning A increases when B decreases.

Tides

affected by the gravitational forces of the Sun and Moon.

Spring Tide

These occur during the full moon and new moon phases, when the Sun and Moon align and exert a combined gravitational pull, resulting in higher high tides.

Neap Tide

These occur during the first quarter and last quarter phases of the moon, when the Sun and Moon are at right angles to each other, resulting in a weaker combined gravitational pull and less difference between high and low tides.

Newtons first law of motion

A stationary object remains still unless pushed or pulled.

Friction

a force that opposes motion. Air molecules act as friction, slowing down objects like bullets. More molecules (e.g., during humid conditions) increase friction

Direct Proportion

Inertia is directly proportional to mass. The more mass an object has, the greater its inertia.