JEE Main Rotational Motion Questions - FREE PDF Download

Rotational Motion covers key concepts like angular displacement, velocity, and acceleration, moment of inertia, torque, angular momentum, and conservation of angular momentum, and they are some of the important topics for JEE Main exams. While going through the previous year's papers of JEE Main, you can find 2 to 4 questions from this chapter. Check out the table below for more information.

Take the chance to elevate your preparation with our Rotational Motion Important Questions. It covers the whole JEE Main Physics syllabus and you can download it for FREE.

JEE Main Rotational Motion Questions 2025 Must-Revise Topics

Let's focus on the key topics you should review in Rotational Motion. These important topics can make a real difference in your preparation. Mastering them while solving the Rotational Motion important questions for JEE Main will give you a strong edge in the upcoming exam. Let's dive into the must-revise topics to help you shine in JEE Main 2025.

• Moment of Inertia

• Angular Velocity and Acceleration

• Torque and Rotational Equilibrium

• Angular Momentum

• Kinematics of Rotational Motion

• Rolling Motion

• Rotational Kinetic Energy

• Combined Translational and Rotational Motion

• Angular Momentum and Torque Relationships

• Conservation of Energy in Rotational Motion

• Angular Momentum and Its Conservation

• Rotational Dynamics

• Angular Impulse and Collision

• Rotational Work and Power

Top Concepts to Study in Rotational Motion JEE Questions 2025

1. Centre of a Mass of a Two-Particle System: Consider it the balance point for two particles. To find this centre, we take into account the individual masses of the particles and their respective positions in space.

The centre of mass is calculated using this formula:

Center of Mass $= \dfrac{m_1 r_1 + m_2 r_2}{m_1 + m_2}$

Here, 'm₁' and 'm₂' represent the masses of the two particles, and 'r₁' and 'r₂' denote their positions. This calculation helps us identify the central point around which the two particles effectively balance, making it a critical concept in understanding rotational motion, equilibrium, and stability.

2. Centre of the Mass of Rigid Body; Basic Concepts of a Rotational Motion; A Moment of Force; Torque:  Think of it as the balance point for the entire object. To calculate it, we consider the distribution of mass within the object and determine the point where the body effectively balances.

Now, let's dive into the concept of rotational motion. It's all about how objects spin and move in a circle. This motion is influenced by a force called torque, which is like a twisting force. Torque is calculated using this formula:

Torque (τ) = Force (F) $\times$ Lever Arm ®

The lever arm is the perpendicular distance from the pivot point to the force's line of action. Torque plays a crucial role in determining how an object rotates or balances, making it a fundamental concept in the study of rotational motion.

3. Angular Momentum: Angular momentum, denoted by 'L,' is the measure of an object's rotation. To understand it, think of a spinning wheel or a planet's orbit. Angular momentum depends on both the object's moment of inertia (how it's distributed in space) and its angular velocity (how fast it's spinning).

The formula for angular momentum is:

Angular Momentum (L) = Moment of Inertia (I) $\times$ Angular Velocity (ω)

Angular momentum helps us comprehend why objects keep spinning, stop, or change their spin. It's an essential concept in studying the dynamic behaviour of rotating systems.

4. Conservation of Angular Momentum and Its Applications: This law is akin to the conservation of linear momentum, but it applies to rotating objects.

The conservation of angular momentum states that in the absence of external torques, the total angular momentum of a system remains constant. In simpler terms, if a rotating object doesn't experience any external twisting forces, its angular momentum won't change. This concept finds applications in various scenarios, such as ice skaters spinning faster by pulling their limbs inward (reducing their moment of inertia) and the behaviour of celestial bodies in space. Understanding the conservation of angular momentum helps us explain and predict the motion of rotating objects in different situations.

5. The Moment of Inertia: It's like the rotational counterpart to mass in linear motion. Moment of inertia denoted as 'I,' quantifies how an object's mass is distributed around its axis of rotation.

Imagine a figure skater spinning. When they bring their arms close to their body, they spin faster. This is because their moment of inertia decreases. The moment of inertia depends on the object's shape and the distribution of its mass. For simple shapes like a rod or a disk, there are mathematical formulas to calculate it. Understanding the moment of inertia is crucial in predicting how objects rotate, and it's a fundamental concept in the study of rotational motion.

6. The Radius of Gyration: Think of it as a measure of how the mass of an object is distributed from its axis of rotation.

The radius of gyration, denoted as 'k,' is a single value that represents the distribution of mass in an object. It's calculated using the formula:

Radius of Gyration (k) = $\sqrt{\dfrac{\text{Moment of Inertia (I)}}{\text{Total Mass (M)}}}$

A smaller radius of gyration means the mass is concentrated closer to the axis of rotation, while a larger radius indicates that the mass is spread out. This concept simplifies complex calculations involving rotation and is essential for understanding how objects behave when they spin.

7. Values of Moments of Inertia for Simple Geometrical Objects: These values are blueprints for how different objects rotate.

For instance, a thin rod rotating about one end has a moment of inertia of $\dfrac{1}{3} (\text{mass}) (\text{length})^2$. A disk rotating around its central axis has a moment of inertia of $\dfrac{1}{2}(\text{mass})(\text{radius})^2$. And for a hoop (like a hula hoop) rotating around its central axis, the moment of inertia is $(\text{mass})(\text{radius})^2$.

These values help us predict how objects will behave when they spin.

8. Parallel and Perpendicular Axes Theorems: the parallel and perpendicular axes theorems are valuable tools for calculating moments of inertia for complex shapes.

The parallel axes theorem states that the moment of inertia about an axis parallel to, but not through, the centre of mass can be found by adding the moment of inertia about an axis through the centre of mass and the product of the object's mass and the square of the distance between the two axes.

The perpendicular axes theorem relates the moments of inertia for an object rotating about two perpendicular axes. It states that the moment of inertia about one axis is equal to the sum of the moments of inertia about two other perpendicular axes through the same point.

• Applications of Parallel Axes Theorem: Rolling Objects: When calculating the moment of inertia for rolling objects like cylinders or spheres, this theorem is essential. It allows us to find the moment of inertia about an axis parallel to the one passing through the centre of mass.

• Composite Objects: For objects composed of multiple simpler shapes, the theorem simplifies the calculation of the total moment of inertia. By finding the individual moments of inertia and using the parallel axes theorem, we can determine the moment of inertia for the composite object.

• Applications of Perpendicular Axes Theorem: Thin Plates and Disks: When dealing with objects like thin plates or disks rotating in a plane perpendicular to their thickness, this theorem is crucial. It helps calculate the moment of inertia about an axis perpendicular to the plane of rotation

• Composite Objects: Just like the parallel axes theorem, the perpendicular axes theorem is useful for composite objects. It simplifies the calculation of the moment of inertia when objects have rotation occurring in two perpendicular directions.

9. Rigid Body Rotation Equation of Rotational Motion: It's akin to Newton's second law but tailored for rotating objects.

The equation states that the net torque acting on an object is equal to the rate of change of its angular momentum. Mathematically, it's expressed as:

Net Torque (τ) = Rate of Change of Angular Momentum $\dfrac{dL}{dt}$

This equation helps us understand how an object's angular motion changes when subjected to torques. It's crucial in predicting and analyzing the behaviour of rotating bodies, allowing us to determine how they accelerate, decelerate, or maintain a constant angular velocity under the influence of various forces.

Learn with Rotational Motion Important Questions and Score High in JEE Main 2025

Mastering Rotational Motion is crucial for JEE Main students who are dedicated to excelling in solving Important Questions. This chapter dives into fundamental concepts such as the angular velocity and torque, which are vital for understanding how objects rotate and are essential for a comprehensive grasp of physics. These concepts are intriguing and hold significant weightage in the JEE Main examination. Here, we will explore why understanding this chapter is essential to successfully tackling JEE Main Important Questions.

Rotational Motion is the field that involves the study of objects' rotation around an axis. The weightage of Rotational Motion in JEE Main is around 4 - 8%, and students can also expect direct questions from this section which makes it one of the scoring topics. Here are the few points that make the chapter high weightage.

Spinning into Understanding:

• Imagine a world beyond linear movement—a world where objects twirl, spin, and pivot. Welcome to the captivating realm of rotational motion!

• Just as we learned about linear motion, rotational motion introduces a dynamic twist as objects rotate around fixed axes. Get ready to unravel the magic of spinning phenomena!

The Dance of Axes and Moments:

• Picture a dancer pirouetting on a stage. Similarly, objects rotate around an axis, creating a mesmerizing ballet. This axis becomes the focal point of rotational motion.

• Ever heard of moments? Not the "take a picture" kind, but moments that describe how objects respond to forces and torques during their graceful spins.

Angular Velocity - The Spin Speedster:

• Meet angular velocity, the speedster of rotation. Just as linear velocity measures how fast an object moves in a straight line, angular velocity measures the rapidity of rotation.

• Think of a spinning top; its angular velocity defines how swiftly it twirls. The concept is as captivating as watching a top gracefully spin.

Torque: The Twisting Force:

• Torque is the superstar that orchestrates rotation. It's the force that creates the twist, making objects pivot around an axis. Imagine turning a doorknob—it's torque that gets the door swinging.

• Torque transforms force into rotation, making it a pivotal concept to master for acing JEE Main.

Moment of Inertia: Unraveling the Resistance:

• Just as mass resists linear acceleration, the moment of inertia opposes rotational acceleration. It's like an object's reluctance to speed up its spin.

• Different shapes have unique moments of inertia. Think of it as objects expressing their preference for spinning dynamics!

Rolling on Fun:

• Wheels rolling smoothly is an everyday example of combined linear and rotational motion. Understanding the mechanics behind rolling unlocks new perspectives.

• Dive into the world of wheels, cylinders, and spheres, and see how they elegantly combine translation and rotation.

Gyroscopic Magic:

• Gyroscopes, those spinning wonders, showcase the extraordinary effects of rotational motion. They defy gravity, maintain stability, and even aid navigation!

• Imagine steering a spacecraft using the gyroscope's magical properties—sounds like something out of a sci-fi adventure, doesn't it?

Visualising with Kinematics:

• Just as we used kinematics for linear motion, now it's time to apply it to rotations. You'll learn equations and concepts to predict the angular journey of spinning objects.

• Imagine tracing the path of a spinning top in your mind—it's kinematics that unravels its graceful dance.

Embark on this engaging voyage into the world of rotational motion. From dancers twirling to wheels rolling, from gyroscopes defying gravity to moments creating spins, every concept in this chapter unveils a captivating facet of physics. Prepare to be enthralled as you explore this dynamic domain, readying yourself for a triumphant journey through JEE Main!

Formula-Memory Connection: Strengthening Knowledge with Rotational Motion Questions JEE

Equations are more than just symbols – They're your secret code to solve problems in Physics. When you understand formulas, you can easily handle tricky ideas and feel more sure of yourself.  Use the equation with JEE Main Rotational Motion Physics Important Questions to improve studying. Check out our JEE Main Physics formula pages and begin your journey to prepare for JEE Main now!

Below are a few important formulas in Rotational Motion. You can also download Vedantu's JEE Main Physics Formulas related to Trigonometry for FREE.

Angular Displacement:
$\theta = \theta_0 + \omega t + \dfrac{1}{2} \alpha t^2$
where $\theta$ = angular displacement, $\theta_0$​ = initial angular displacement, $\omega$ = initial angular velocity, $\alpha$ = angular acceleration, and t = time.

Angular Velocity:
$\omega = \omega_0 + \alpha t$
where $\omega$ = angular velocity, $\omega_0$​ = initial angular velocity, $\alpha$ = angular acceleration, and t = time.

Angular Kinetic Energy:
$K = \dfrac{1}{2} I \omega^2$
where I = moment of inertia, $\omega$ = angular velocity.

Moment of Inertia:
$I = \sum m_i r_i^2$
where $m_i$​ = mass of the particle and $r_i$ = distance from the axis of rotation.

Torque:
$\tau = I \alpha$
where $\tau$ = torque, I = moment of inertia, and $\alpha$ = angular acceleration.

Rotational Work Done:
$W = \tau \theta$
where W = work done, $\tau$ = torque, and $\theta$ = angular displacement.

Rotational Power:
$P = \tau \omega$
where P = power, $\tau$ = torque, and $\omega$ = angular velocity.

Rotational Dynamics Equation:
$\tau = I \alpha$
where $\tau$ is the torque, I is the moment of inertia, and $\alpha$ is the angular acceleration.

Relation Between Linear and Angular Quantities:

• $v = r \omega$ (Linear velocity to angular velocity)

• $a = r \alpha$ (Linear acceleration to angular acceleration)

• $F = \tau / r$ (Force and torque relation)

Conservation of Angular Momentum:
$L = I \omega$
where L = angular momentum, I = moment of inertia, and $\omega$ = angular velocity.

Achieve Success Through Vedantu’s Rotational Motion Important Questions for JEE Main PDF 

The Rotational Motion Important Questions PDF serves as an invaluable tool for comprehending the intricate principles of rotational motion in physics. This resource, carefully crafted with questions spanning different difficulty levels, reinforces core concepts while nurturing effective problem-solving skills. With detailed solutions provided in JEE Main Rotational Motion Important Questions, it bridges the gap between theory and practical application, making the subject more accessible. By embracing this resource, students can confidently tackle the complexities of rotational motion, ensuring a strong grasp of the subject and excelling in their academic endeavors. It's a valuable aid in simplifying the often challenging world of rotational physics.

JEE Mains PYQ Chapterwise: Mastering Rotational Motion with Past Papers

Conquering JEE Mains requires unwavering dedication and strategic preparation. One invaluable tool in your arsenal is the treasure trove of previous year question papers (PYQs). But navigating those years of questions can be overwhelming, especially for a crucial chapter like Rotational Motion. Enter JEE Mains PYQ Chapterwise: your key to targeted practice and exam mastery in this foundational subject.

By delving into JEE Main Chapter-wise PYQs for Rotational Motion, you gain laser-sharp focus on specific topics within this crucial domain. Imagine tackling your weakest areas, with a targeted set of past questions, building confidence and competence one problem at a time.

Whether you prefer the convenience of a JEE Mains Previous Year Questions Chapter Wise for Rotational Motion with PDF download or prefer working directly from online resources, the benefits are undeniable. You'll hone your problem-solving skills, learn to apply theoretical knowledge to real-world scenarios involving Rotational Motion, and develop the exam temperament needed to excel under pressure, especially when faced with Rotational Motion questions. Remember, these questions are like blueprints for future JEE Mains papers – studying them is like peeking into the exam itself!

So, unleash the power of JEE Main PYQ Chapterwise for Rotational Motion. Download your chosen resources, pick your weakest topic within this chapter, and start practicing. Each solved question is a step closer to your JEE Mains dream. Remember, consistency is key! Make chapterwise PYQs for Rotational Motion a daily ritual, and watch your confidence and competence soar as you approach the exam with a laser-sharp focus and a wealth of knowledge at your fingertips, ready to conquer even the most challenging topics in Rotational Motion.

Supplementary Resources for JEE Main 2025 Rotational Motion

Looking to enhance your Rotational Motion JEE Main Questions preparation? Explore these Important materials, with these tools to improve comprehension and test-taking skills, improving your JEE Main 2025 performance!

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