# forces in the universe what is a force? what is a force? a push or a pull

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Bouyancy

Forces in the Universe

The action of change in the Universe comes through forces. Understanding forces can help you know how the Universe works.1What is a force?

This brings up the question: What is a force?2What is a force?

A push or a pull

The easy answer is that a force is a push or a pull. Another questions would be what causes a push or pull, and that will be addressed at the end of this podcast.3Isaac Newton

Much of what we know about the universe comes from the work of Isaac Newton.4Isaac Newton3 Laws of MotionInvented CalculusUniversal GravityReflecting Telescope

Newton wanted to explain why the Moon went around the Earth. To do this, Newton came up with the three laws of motion. He needed a new kind of math to explain motion, so he invented calculus. This led to the mathematical rules that explain how gravity works everywhere in the Universe. He also invented the reflecting telescope.5Isaac Newton3 Laws of MotionInvented CalculusUniversal GravityReflecting Telescopein about one year

Oh, and he did all of these things in about a year. 61st Law of Motion: the law of inertia

The 1st law of motion is sometimes called the law of inertia.71st Law of Motion: the law of inertia

An object at rest will remain at rest unless acted on by an outside force. An object in linear motion will remain in linear motion unless acted on by an outside force.

One way to describe this law is to say that everything in the universe likes to keep doing what it is doing. Inertia is the measure of how much an object resists changes to its motion.82nd Law of Motion:

The second law of motion can be most easily explained or even remembered with a famous mathematical equation.9

Newton described the acceleration or change in motion of an object as being directly dependent on how hard you pushed it. He also said that the acceleration would be inversely proportional to the mass of the object. This means the bigger it is, the less it will accelerate.10

Combine these two and you get force equals mass times acceleration, F = ma113rd Law of Motion: the law of rockets

The 3rd law can be used to explain how rockets work.123rd Law of Motion: the law of rockets

For every action, there is an equal and opposite reaction.

Here is the third law in words. It can also be stated that it is impossible to touch something without being touched yourself.133rd Law of Motion: how do rockets work?

A rocket works by containing a chemical reaction that ejects gases from the bottom end of the rocket. The action is the ejection of the gases at high speed. The reaction is an equal but opposite force on the rocket upward. The ejected gas does not push against an atmosphere.

So, how does a rocket work? The chemical reaction and design of the rocket force gases at high speed to be pushed out of the rocket. This push results in an equal and opposite reaction the rocket goes upward.14

3rd Law of Motion:

You jump off of a step. You fall due to the force of gravity. How does Newtons 3rd law apply?

Imagine that you jump off of a step and you are in mid-air. There is a force on you and you would know this because you are being accelerated downward due to the downward force of gravity. If this is the action, what is the reaction? 163rd Law of Motion:

You jump off of a step. You fall due to the force of gravity. How does Newtons 3rd law apply?

The reaction is that you pull up on the Earth with the same force that you are pulled down. So, why doe the Earth not come up to meet you halfway whenever you fall? The 3rd law says that the force is equal, but not the acceleration. Force is the product of mass times acceleration. Since the earth is so big, it can have a really really small accelertion that is not measurable. But it does happen!17Four known forces in the Universe1.

2.

3.

4. Gravity attraction between all objects of mass

So why do things get pushed or pulled? There are 4 known reasons for pushes or pulls. The weakest force in the Universe is gravity. Gravity is the force between all objects of mass, big and small. You are attracted to this computer monitor as well as to the Earth and the planet Mars.18Four known forces in the Universe1.

2.

3. Weak Nuclear causes isolated neutrons to decay, source of radioactivity

4. Gravity attraction between all objects of mass

19Four known forces in the Universe1.

2. Electricity & Magnetism interaction of property of matter called charges

3. Weak Nuclear causes isolated neutrons to decay, source of radioactivity

4. Gravity attraction between all objects of mass

Four known forces in the Universe1. Strong nuclear short range force that binds protons together in the nuclei of atoms

2. Electricity & Magnetism interaction of property of matter called charges

3. Weak Nuclear causes isolated neutrons to decay, source of radioactivity

4. Gravity attraction between all objects of mass

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