The 'Goes Up Must Come Down' Law: Shocking Science!
Newton's Law of Universal Gravitation, a cornerstone of classical physics, rigorously articulates what goes up must come down law. NASA's deep space exploration program constantly grapples with the implications of this law in trajectory planning and orbital mechanics. The Cavendish Experiment provided critical empirical validation supporting the mathematical framework that underpins what goes up must come down law. Understanding this fundamental principle also allows us to better comprehend potential impacts from near-Earth objects, making it crucial in various scientific fields.
Image taken from the YouTube channel StarTalk , from the video titled Neil deGrasse Tyson Explains "What Goes Up, Must Come Down" .
Understanding the "What Goes Up Must Come Down Law": A Scientific Look
The phrase "what goes up must come down law" is deeply ingrained in our everyday language. It expresses an intuitive understanding of gravity, but a deeper exploration reveals the fascinating physics at play. This article dissects the meaning behind the phrase, connecting it to the scientific principles that govern motion and the force of gravity.
The Foundation: Gravity
The "what goes up must come down law" is fundamentally about gravity.
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What is Gravity? Gravity is a force that attracts any two objects with mass. The more mass an object has, the stronger its gravitational pull.
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Earth's Gravity: The Earth's immense mass exerts a powerful gravitational pull, constantly drawing everything towards its center. This is why things fall to the ground.
Defining "What Goes Up"
To understand the "what goes up must come down law", we need to define what it means for something to "go up".
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Applying Force: Overcoming gravity requires applying an upward force that is greater than the downward pull of gravity. Think of throwing a ball: your arm provides the initial force.
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Initial Velocity: This upward force imparts an initial velocity to the object, causing it to move upwards.
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Kinetic Energy: The object now possesses kinetic energy – the energy of motion. This energy is what allows it to travel against gravity.
The Trajectory: A Battle Against Gravity
As the object moves upward, gravity is constantly working against it.
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Deceleration: Gravity causes the object to decelerate – its upward velocity decreases over time.
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Energy Conversion: The object's kinetic energy is gradually converted into potential energy – stored energy related to its position in a gravitational field. The higher the object goes, the more potential energy it gains.
The Apex: The Turning Point
Eventually, the object reaches a point where its upward velocity becomes zero. This is the apex of its trajectory.
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Potential Energy Maximum: At the apex, the object possesses its maximum potential energy and zero kinetic energy.
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Brief Pause: The object momentarily pauses before beginning its descent. This "pause" isn't actually static. Instead, the direction is in the process of changing.
The Descent: Gravity Takes Over
With zero upward velocity, the object begins to fall back down.
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Acceleration: Gravity now accelerates the object downwards, increasing its velocity.
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Potential Energy to Kinetic Energy: The object's potential energy is converted back into kinetic energy as it falls.
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Increasing Velocity: The object falls faster and faster until it encounters air resistance.
The Role of Air Resistance
While gravity is the primary force at play, air resistance also plays a role, especially for objects with a large surface area.
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Opposing Force: Air resistance is a force that opposes the motion of an object through the air.
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Terminal Velocity: As an object falls, air resistance increases until it equals the force of gravity. At this point, the object reaches its terminal velocity – a constant falling speed.
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Impact on Lightweight Objects: Air resistance has a more significant impact on lightweight objects with large surface areas, such as feathers or paper, causing them to fall much slower than denser objects.
Beyond Earth: A Universal Principle?
While the phrase is Earth-centric, the underlying principle extends beyond our planet.
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Gravity in the Universe: Gravity is a fundamental force throughout the universe, affecting the motion of planets, stars, and galaxies.
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Varying Gravitational Forces: The strength of gravity varies depending on the mass and distance between objects. For example, the Moon has less gravity than the Earth, so an object thrown upwards on the Moon would reach a greater height and fall back down more slowly.
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Newton's Law of Universal Gravitation: Isaac Newton formalized our understanding of gravity with his Law of Universal Gravitation, which states that every particle attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Video: The 'Goes Up Must Come Down' Law: Shocking Science!
FAQs: The 'Goes Up Must Come Down' Law
These frequently asked questions aim to clarify some common points about the principle we often call "The 'Goes Up Must Come Down' Law".
What exactly does "The 'Goes Up Must Come Down' Law" mean?
Simply put, "what goes up must come down law" is a less formal way of stating that gravity exerts a force that pulls objects towards each other. In the context of Earth, it means anything launched upwards will eventually be pulled back down.
Is this law always true? Are there exceptions?
For most practical situations on Earth, it's true. The main exception is if an object reaches escape velocity. Escape velocity is the speed needed to overcome Earth's gravitational pull.
What force is responsible for the "goes up must come down" phenomenon?
The primary force at play is gravity. Earth's gravity constantly acts on objects, drawing them towards its center. This is why anything thrown into the air eventually falls back down.
Does "what goes up must come down law" apply to things like helium balloons?
Not in the same direct way. Helium balloons rise because they are lighter than the surrounding air. They stop rising when they reach an altitude where the surrounding air has the same density. Eventually, they also descend, often due to helium leaking out, increasing their overall density.