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The Gravitational Force
Sir Isaac Newton described gravity and hypothesized that the force that causes objects to fall to the ground is the same force which keeps the Earth orbiting the sun. This discovery has been considered one of the greatest single contributions to science in the whole of human history.
The gravitational force of nature is a non-contact force of attraction between two bodies with mass.
Since gravity is a non-contact force it can act over two objects that are not physically touching, even at large distances! Let's see how it works in a bit more detail. To understand how gravity works it is useful to introduce the concept of the center of mass.
We can assume that the whole mass of an object is located at a single point. This point is known as the center of mass and its location depends on how the mass is distributed in the object.
Try manipulating an object in your hand and see if you can determine its center of mass. This will help you gain intuition about the concept.
The center of mass of a sphere is located in its geometrical center. In an average person, it is slightly below the navel.
The theory of gravity states that every mass in the universe attracts every other object by an invisible force acting along the direction of the line joining both objects' centers of mass. The force between the two objects depends on their masses and the distance between their centers of mass.
The more massive an object, the greater the attractive force it exerts on other massive objects. We do not see a bunch of pencils on a table jumping towards each other because their gravity is far too small to be noticed since their mass is so small. On the other hand, this effect becomes noticeable for very massive objects like the planets in our solar system. For example, the moon keeps in its orbit around the earth because of the gravitational force between them.
Now let's look at another force that is very similar to gravity but acts on a much smaller scale i.e. on the subatomic scale.
Strong Nuclear Force
The strong nuclear force is a subatomic force that holds together the nucleus of every atom in the universe.
This force forms the basis of every element that we see in our lives. As we know, an atom is made up of a nucleus where most of its mass is concentrated and electrons that orbit the nucleus. The magnitude of the strong force has to be large enough to hold the nucleus against the massive repulsive electromagnetic force between the protons. To put its strength into perspective, The magnitude of the force is \(6\times10^{39}\) times as strong as the force of gravity on earth.
The strong force actually holds together the quarks as clusters which form more-familiar subatomic particles like the protons and neutrons. The quark is a fundamental particle that constitutes matter. Quarks together combine to form particles like neutrons and protons. Quarks are of 6 types up, down, charm, strange, top and bottom.
However, a strong nuclear force can only act at very small distances around the range of approximately \(10^{-15}\mathrm m\). This is also roughly the diameter of the proton.
Weak Nuclear Force
The weak nuclear force is a weak interaction at the subatomic level that is responsible for the radioactive decay of nuclei.
Beta particles are emitted as fast-moving electrons \(\mathrm e-\). But the nucleus does not house any electrons. So then where do they come from? Beta particles are created when a neutron transforms into a proton and an electron. This electron is then emitted from the nucleus. The mass of a \(\mathrm\beta\) particle is relatively small. It can therefore be represented by the following symbol \({}_{-1}^0\mathrm\beta\).
The potassium isotope decays into calcium by undergoing beta radiation.
$${}_{19}^{40}\mathrm K\rightarrow{}_{20}^{40}\mathrm{Ca}\;+\;\mathrm e^{-1}$$
We can see that the mass number has been unchanged but the atomic number has gone up due to the loss of an electron.
The above nuclear reaction is possible due to the weaker counterpart of the strong nuclear force. There is a lot of importance for this force because this is what makes the nuclear reaction in the sun possible. The nuclear fusion that powers the sun. The weak force is stronger than gravity but only effective over a distance of \(10^{-18}\;\mathrm m\), it's strength is closest to that of the electromagnetic force. The weak force, or weak interaction, is stronger than gravity, but it is only effective at very short distances. It acts on the subatomic level and plays a crucial role in powering stars and creating elements. This brings us to the last of the fundamental forces, the electromagnetic force of nature.
Electromagnetic Force
The electromagnetic force is the force of attraction and repulsion experienced between charged particles, that is, particles which have the property of charge.
The electromagnetic force is made of two components, The electric component and the magnetic component. Let's look at an example where we can see this force in action. The electromagnetic force is active over an infinite range.
If you suspend a magnet by a thread it will align itself in such a way that it will point towards the geographic north pole. This effect is due to the electromagnetic force.
Have you ever wondered how an electromagnet works? It works on the principle of electromagnetism. A current-carrying conductor will produce a magnetic field around it. This magnetises the head of the electromagnet and this enables it to carry metal components.
The opposite happens when a magnetic field interacts with a wire i.e it induces a current.
The direction of the magnetic field produced can be found using Fleming's left-hand rule.
The rule states that if we stretch the thumb, middle finger, and index finger of the left hand in such a way that they make an angle of 90 degrees. Then the thumb will point in the direction of the induced force \((F)\)the middle finger will point in the direction of the current \((I)\)and the Index finger will represent the direction of the magnetic field \((B)\).
An easy way to remember this is by using the acronym FIB, where the letters stand for the properties defined above. The letters represent each of the fingers starting from the thumb and ending at the middle finger. Another law that can help us find the
The right-hand thumb rule can be used in conjunction with the above rule in finding the directions of the current or magnetic field.
The rule states that if you hold a current-carrying conductor with the thumb pointed in the direction of the flow of current, then the direction in which the fingers curl will represent the magnetic field around it.
Let us now look at an example where all of these fundamental forces act.
Look at the above example of a kid playing basketball, the ball hits the ground due to the force of gravity acting on the atoms of the rubber which the ball is made from. These atoms are held together due to the strong nuclear force of attraction. The interaction between the molecules and ions of the materials that were used to manufacture the ball is governed by the electromagnetic force.
This brings us to the end of the article. Let's now go through what we've learned so far. The below image gives a quick overview of the four fundamental forces and some of their properties. The content of the image goes beyond what you will be expected to know about high school physics, but that doesn't mean you might not find it interesting or useful!
Overview of the fundamental forces in nature and how they compare against each other with respect to strength and range, Hyper Physics
Forces of Nature Physics - Key takeaways
- All the phenomena in this universe can be explained by the four fundamental forces.
- They are the gravitational force, weak nuclear force, strong nuclear force and the electromagnetic force.
- The gravitational force of nature is a non-contact force of attraction between two bodies with mass.
- The strong nuclear force of nature is a subatomic force that holds together the nucleus of every atom in the
- universe.
- The weak nuclear force is a weak interaction at the subatomic level that is responsible for the radioactive decay of nuclei.
- The electromagnetic force of nature is a force of attraction and repulsion between charges.
- The strongest fundamental force is the strong nuclear force. The weakest fundamental force is the gravitational force of nature.
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Frequently Asked Questions about Forces of Nature Physics
What is the meaning of forces of nature?
Forces of nature are the four fundamental forces that govern the universe. They are the gravitational force, weak and strong nuclear forces and the electromagnetic force.
Why gravitational force is the weakest force in nature?
The gravitational force of nature is the weakest force in nature because it requires a very large body of mass to create a high magnitude of force. Another factor is the distance. Due to the large distances between celestial bodies the gravitational force between most bodies is weak.
Which is the weakest force in nature?
The gravitational force is the weakest force in nature.
What is the strongest force in nature?
The strongest force in nature is the strong nuclear force.
What are examples of forces of nature?
The force that holds a nucleus together, the gravitational force of attraction between the earth and the moon which keeps it in orbit, are both examples of forces in nature.
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