The laws of physics are fundamental principles that describe the behaviour of matter and energy in the universe. There are different Laws in physics and , here can find one place where you can learn all the Laws of Physics in one place.
In this blog, we have added 12 Laws of Physics and explained them in a simple format, so that you can understand the law and its meaning. To check the rest of the laws and detailed explanation click here.
Laws of Physics
1. Newton’s First Law of Motion:
An object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity, unless acted upon by an external force.
Example: A book on a table will remain at rest until someone applies a force to move it.
2. Newton’s Second Law of Motion:
The acceleration of an object is directly proportional to the force applied to the object and inversely proportional to its mass.
Example: Pushing a shopping cart requires more force to accelerate if it is filled with groceries than if it is empty.
3. Newton’s Third Law of Motion:
For every action, there is an equal and opposite reaction.
Example: When a ball is thrown against a wall, the force applied by the ball to the wall is equal in magnitude and opposite in direction to the force applied by the wall on the ball.
4. Law of Conservation of Energy:
Energy cannot be created or destroyed, only transformed from one form to another.
Example: When a ball is thrown, its kinetic energy is transformed into potential energy as it reaches its maximum height and then back into kinetic energy as it falls back to the ground.
5. Law of Conservation of Mass:
Matter cannot be created or destroyed, only transformed from one form to another.
Example: When wood burns, the wood is transformed into ash and gases, but the total mass of the burning wood and the resulting ash and gases remains constant.
6. Laws of Thermodynamics:
The study of energy and heat transfer.
First Law: Energy cannot be created or destroyed, only transferred or converted from one form to another.
Second Law: The total entropy (disorder) of a closed system cannot decrease over time.
Third Law: The entropy of a system approaches a constant value as its temperature approaches absolute zero.
Example: A refrigerator cools food and transfers heat to the surroundings, but the total amount of energy remains constant according to the first law of thermodynamics.
7. Lambert’s Cosine Law
Lambert’s cosine law is a scientific principle that describes the relationship between the illumination of a surface and the cosine of the angle between the direction of incident light and the surface normal. This law is named after Johann Heinrich Lambert and was formulated in 1760. A surface that follows Lambert’s law appears equally bright from any angle and exhibits Lambertian reflectance.
An example of this law in action would be a piece of paper that appears the same brightness when viewed from any angle, due to its diffuse reflection of light. This law is commonly used in areas such as radiometry and computer graphics.
8. D’Alembert’s Principle
D’Alembert’s principle is a scientific principle, describes the relationship between the forces acting on a mass particle and the rate of change of momentum of the system itself along any virtual displacement. Simply put, the sum of the differences between the forces acting on the mass particle and the rate of change of momentum of the system is zero.
For example, imagine two teams playing tug-of-war. The force acting on the rope is the sum of the forces applied by both teams and the acceleration is calculated accordingly. Another example involves a box on an inclined surface with friction, where the forces acting on the box due to friction and gravity are taken into account to calculate the acceleration.
9. Hubble’s Law
Hubble’s Law is a fundamental principle in astrophysics that describes the relationship between the distance of a galaxy from Earth and its velocity of recession. It states that the farther a galaxy is from Earth, the faster it is moving away from us.
This relationship is expressed mathematically as v = H0d, where v is the velocity of recession, d is the distance to the galaxy, and H0 is the Hubble constant, which represents the rate of expansion of the universe.
An example of Hubble’s Law in action is the observation of the Andromeda Galaxy. By measuring its distance from Earth using various techniques, astronomers have determined that it is approximately 2.5 million light-years away. They have also measured its velocity of recession using the Doppler effect, which involves observing the shift in the wavelength of light emitted by the galaxy. The result is that Andromeda is moving away from us at a velocity of approximately 300 kilometers per second. This observation confirms Hubble’s Law, as the velocity of recession is proportional to the distance of the galaxy from Earth.
10. What is Boltzmann Equation
The Boltzmann equation is a fundamental equation in statistical mechanics that describes the behaviour of a gas at the molecular level. It is used to model the interactions between particles in a gas and predict macroscopic properties such as temperature, pressure, and density. The equation is named after Austrian physicist Ludwig Boltzmann, who developed it in the late 19th century.
The Boltzmann equation is a partial differential equation that describes the evolution of the probability distribution function of particles in a gas. It takes into account the collisions between particles and the forces acting on them.
The equation can be used to calculate the distribution of velocities of particles in a gas, which in turn can be used to calculate macroscopic properties such as temperature and pressure.
An example of the Boltzmann equation in action is the calculation of the thermal conductivity of a gas. The thermal conductivity is a measure of how well a material conducts heat.
It can be calculated using the Boltzmann equation by modeling the interactions between particles in the gas and the transfer of heat energy through collisions. The resulting equation can be used to predict the thermal conductivity of a gas under different conditions, such as changes in temperature or pressure.
11. Beer-Lambert Law
The Beer-Lambert Law is a fundamental principle in spectroscopy that describes the relationship between the concentration of a solution and the amount of light absorbed by that solution. August Beer and Johann Lambert discovered the law in the 19th century.
The law states that the absorbance of a solution is directly proportional to the concentration of the absorbing species and the path length of the light through the solution.
Mathematically, the law can be expressed as A = εcl, where A is the absorbance, ε is the molar absorptivity (a constant that depends on the absorbing species and the wavelength of light), c is the concentration of the absorbing species, and l is the path length of the light through the solution.
An example of the Beer-Lambert Law in action is the measurement of the concentration of a colored compound in a solution using a spectrophotometer. The spectrophotometer measures the amount of light absorbed by the solution at a specific wavelength, and the absorbance is then used to calculate the concentration of the compound using the Beer-Lambert Law.
This technique is commonly used in analytical chemistry and biochemistry to measure the concentration of compounds such as proteins, nucleic acids, and pigments in a solution.
12. Van Der Waals Equation
The Van der Waals equation is a state equation that describes the behavior of real gases, taking into account the non-ideal behavior of gas molecules and the interactions between them. It was developed by Dutch physicist Johannes Diderik van der Waals in the late 19th century.
The equation incorporates two corrections to the ideal gas law: the first correction accounts for the finite size of gas molecules, which reduces the available space for the gas to occupy, and the second correction accounts for the attractive forces between gas molecules.
The equation is written as (P + a(n/V)^2)(V – nb) = nRT, where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of gas, R is the gas constant, T is the temperature of the gas, a is a measure of the attraction between gas molecules, and b is a measure of the size of the gas molecules.
An example of the Van der Waals equation in action is the calculation of the critical temperature and pressure of a gas. The critical temperature and pressure are the conditions at which the gas can no longer be liquefied by increasing the pressure at a constant temperature.
The Van der Waals equation can be used to calculate these values for a given gas by solving for the values of T and P at which the first and second derivatives of the equation with respect to V are zero. This information is important in the design and operation of industrial processes involving gases, such as the production of liquefied natural gas.
You can find other Laws of physics in our next Blog. Want to read about a specific topic not mentioned above, comment below.