What Is Kinetics? Definition, Laws, and Solved Problems Explained
In physics, the study of objects is divided into mechanics. Mechanics have further been divided into two branches of study dynamics and statics. In the dynamic branch of mechanics, the particles in motion or the bodies in motion under forces’ action are studied. In this dynamics branch of mechanics, the study deals with bodies and objects that do not undergo any change in motion, that is they are moving at a uniform motion or are in equilibrium even with an application of force or torque. The dynamic mechanics is further divided into two parts for studying Kinetics and kinematics. They are also referred to as Kinetics Dynamics and Kinematics Dynamics.
Kinetics Dynamics and Kinematics Dynamics
Often the terms Kinetics Dynamics and Kinematics Dynamics creates confusion in students' minds more so because Kinetics is also a branch of study in chemistry and biochemistry that deals with the progress of reactions. Whereas the branch of Kinetics in Physics is entirely different from the one in chemistry, let us learn more about it and its differences. It is important to note that both Kinetics Dynamics and Kinematics Dynamics fall under one umbrella of Dynamics Mechanics.
Kinetics and Kinetic Energy
Kinetics study deals with the movement of objects and that is due to kinetic energy and this can be classified into three different types. And this mainly deals with change in mass and velocity that will change depending on the type of object that is the mass of an object and the velocity of the change in motion due to force applied. Mass is represented as ‘m’ and velocity is represented by ‘v’. Even though kinetics has no specific formula the kinetic energy can be calculated using-
Ek = ½ mv2
The rotational kinetic energy- this kind of energy is seen when the object is in the rotation of an object on an axis of the object. It is also called angular momentum or angular kinetic energy. The energy can also be possessed by the objects like the top moving in circles, or planets moving around the sun, so to study such objects in motion one has to use the method of rotational kinetic energy.
Vibrational Kinetic energy- Vibrational energy as the name suggests is possessed by objects which vibrate when a force is applied for example when phone rings and the other instance one can see is when one beats a drum it vibrates.
Translational Kinetic energy- this kind of kinetic energy is seen when an object is already in motion and with a certain amount of force applied it moves from one place to another the energy force is transferred and translated as the change in velocity.
Kinetics in Everyday Life
Kinetics and kinetic energy can be seen and experienced in our everyday lives as well. Certain examples are-
It can be seen in hydropower plants, in here due to the kinetic energy of the water the plants can generate electricity.
Generation of electricity with the help of windmills which are in motion.
Moving cars possess kinetic energy.
The motion of a bullet since force is applied via the gun possesses kinetic energy.
Cycling as we apply force for the movement of pedals. Pedalling scents the bicycle in kinetic motion.
Conclusion
Kinetics is very important for the objects in motion or the dynamic objects. It has been an important mode of study in the field of physics ever since its discovery and is not subsiding anytime soon. We can find many answers to the questions of movement and mechanics through kinetics.
FAQs on Kinetics in Physics: Concepts, Formulas & Applications
1. What is kinetics in the context of physics?
In physics, kinetics is a branch of classical mechanics that studies the motion of objects while considering the causes of that motion, namely forces and torques. It connects the forces acting on an object to the resulting change in its motion (acceleration), fundamentally answering 'why' an object moves the way it does.
2. How does kinetics differ from kinematics?
The key difference lies in what is being studied. Kinematics describes motion (position, velocity, acceleration) without considering its causes. It answers 'how' an object moves. In contrast, kinetics studies the relationship between motion and its causes (force, mass), answering 'why' an object's motion changes. For example, kinematics would describe a ball's trajectory, while kinetics would analyse how the force of the throw and gravity created that trajectory.
3. What are the fundamental principles that govern kinetics?
The study of kinetics is built upon Newton's Laws of Motion. These three principles form the bedrock for analysing how forces affect the motion of objects:
- Newton's First Law (Law of Inertia): An object remains at rest or in uniform motion unless acted upon by a net external force.
- Newton's Second Law (F=ma): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
- Newton's Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.
4. What are the main types of motion analysed in kinetics?
Kinetics analyses the forces and torques causing different types of motion. The primary categories are:
- Translational Motion: The movement of an object's centre of mass from one point to another, caused by net forces. Example: A box being pushed across a floor.
- Rotational Motion: The movement of an object around a fixed axis, caused by net torques. Example: A spinning wheel.
- General Plane Motion: A combination of both translational and rotational motion. Example: A ball rolling down a hill.
5. What is the relationship between kinetics and dynamics in classical mechanics?
Dynamics is the broad study of objects in motion and the forces that cause this motion. It is typically divided into two sub-branches: kinematics (the description of motion) and kinetics (the analysis of the causes of motion). However, in many modern physics and engineering contexts, the terms 'dynamics' and 'kinetics' are used interchangeably to refer specifically to the study of forces causing motion.
6. Why is Newton's Second Law (F=ma) considered the foundational equation of kinetics?
Newton's Second Law is the cornerstone of kinetics because it provides the direct, quantitative link between the cause (net force, F) and the effect (acceleration, a), mediated by the object's intrinsic property of mass (m). This single equation allows us to predict an object's future motion based on the forces applied to it, which is the central problem that kinetics aims to solve.
7. How is kinetics applied in real-world engineering, such as designing safer cars?
Kinetics is crucial for safety engineering. When designing cars, engineers use principles of kinetics to analyse forces during a collision. For example, crumple zones are designed to deform over a specific time, increasing the duration of impact. According to kinetic principles (related to impulse), increasing the time it takes for the car to stop reduces the average impact force experienced by the passengers, thereby enhancing safety.
8. What key quantities does kinetics analyse that kinematics ignores?
Kinetics focuses on the 'why' of motion and therefore analyses several quantities that kinematics completely ignores. The most important of these are:
- Force: The push or pull that can change an object's state of motion.
- Mass: A measure of an object's inertia or resistance to acceleration.
- Momentum: The product of an object's mass and velocity, quantifying its motion.
- Torque: The rotational equivalent of force, which causes an object to rotate.
