Kinematics Class 11 Physics Notes

Kinematics is the study of motion as a function of time, without considering the forces causing motion.

Key Concepts

Rest

• An object is at rest if it doesn't change its position with respect to a reference point.

Motion

• An object is in motion if it changes its position with respect to a reference point.

Motion in a Straight Line

Distance

• Total length of the path traveled by an object from its initial to final position.
• Scalar quantity, can never be zero.
• Unit: meter (m).

Displacement

• Shortest distance between two points in a specified direction.
• Vector quantity, can be zero.
• Unit: meter (m).

Speed

• Rate of change of distance with time.
• Scalar quantity.
• Unit: m/s.

Types of Speed

• Average Speed: Total distance divided by total time.
• Uniform Speed: Equal distances covered in equal intervals of time.
• Non-uniform Speed: Unequal distances covered in equal intervals of time.
• Instantaneous Speed: Speed at a very small interval of time.

Velocity

• Rate of change of displacement with time.
• Vector quantity.
• Unit: m/s.

Types of Velocity

• Average Velocity: Total displacement divided by total time.
• Uniform Velocity: Equal displacements in equal intervals of time.
• Non-uniform Velocity: Unequal displacements in equal intervals of time.
• Instantaneous Velocity: Velocity at a very small interval of time.

Acceleration

• Rate of change of velocity with time.
• Vector quantity.
• Negative acceleration is called retardation (deceleration).

Equations for Uniform Acceleration

1. ( v = u + at )
2. ( S = ut + \frac{1}{2}at^2 )
3. ( v^2 = u^2 + 2as )

Graphical Treatment

Displacement-Time Graph

• Slope represents velocity.

Velocity-Time Graph

• Slope represents acceleration.
• Area under the graph represents displacement.

Projectile Motion

Key Features

• Object moving under gravity alone.
• Path is a parabola.

Important Parameters

• Maximum Height: ( H_{max} = \frac{u^2 \sin^2 \theta}{2g} )
• Time of Flight: ( T = \frac{2u \sin \theta}{g} )
• Horizontal Range: ( R = \frac{u^2 \sin 2\theta}{g} )_

Projection Angles

• Maximum horizontal range at ( \theta = 45^\circ ).

Relative Velocity

• Velocity of one object with respect to another.

Numerical Problems and Examples

• Examples are provided to illustrate calculations of distance, displacement, projectile motion parameters, and relative velocity.

By understanding these fundamental concepts, students can solve problems related to motion in one dimension, projectile motion, and relative velocity. This forms the basis for further studies in dynamics and other physics topics.