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Kinematics Class 11 Notes Physics

  • Inertial frame of reference:- Reference frame in which Newtonian mechanics holds are called inertial reference frames or inertial frames. Reference frame in which Newtonian mechanics does not hold are called non-inertial reference frames or non-inertial frames.
  • The average speed vav and average velocityKinematics Class 11 Notes Physicsof a body during a time interval ?t is defined as,
    vav = average speed
    = ?s/?t
    Kinematics Class 11 Notes Physics
  • Instantaneous speed and velocity are defined at a particular instant and are given by
    Kinematics Class 11 Notes Physics
    Note:
    (a) A change in either speed or direction of motion results in a change in velocity
    (b) A particle which completes one revolution, along a circular path, with uniform speed is said to possess zero velocity and non-zero speed.
    (c) It is not possible for a particle to possess zero speed with a non-zero velocity.
  • Average acceleration is defined as the change in velocity  Kinematics Class 11 Notes Physics  over a time interval ?t.  
    Kinematics Class 11 Notes Physics
    The instantaneous acceleration of a particle is the rate at which its velocity is changing at that instant.
  • The three equations of motion for an object with constant acceleration are given below.
    (a) v = u+at
    (b) s = ut+1/2 at2
    (c) v2 = u2+2as
    Here u is the initial velocity, v is the final velocity, a is the acceleration, s is the displacement travelled by the body and t is the time.
    Note: Take ‘+ve’ sign for a when the body accelerates and takes ‘–ve’ sign when the body decelerates.
  • The displacement by the body in nth second is given by,
    sn = u + a/2 (2n-1)
  • Position-time (x vs t), velocity-time (v vs t) and acceleration-time (a vs t) graph for motion in one-dimension:
    (i) Variation of displacement (x), velocity (v) and acceleration (a) with respect to time for different types of motion.  
     
    Displacement(x)
    Velocity(v)
    Acceleration (a)
    (a) At rest
     Kinematics Class 11 Notes Physics
     
     Kinematics Class 11 Notes Physics
     
     Kinematics Class 11 Notes Physics
    (b) Motion with constant velocity
      Kinematics Class 11 Notes Physics

      Kinematics Class 11 Notes Physics

      Kinematics Class 11 Notes Physics
    (c) Motion with constant acceleration
      Kinematics Class 11 Notes Physics
      Kinematics Class 11 Notes Physics

      Kinematics Class 11 Notes Physics
    (d) Motion with constant deceleration
      Kinematics Class 11 Notes Physics

      Kinematics Class 11 Notes Physics

    Kinematics Class 11 Notes Physics

  • Scalar Quantities:- Scalar quantities are those quantities which require only magnitude for their complete specification.(e.g-mass, length, volume, density)
  • Vector Quantities:- Vector quantities are those quantities which require magnitude as well as direction for their complete specification. (e.g-displacement, velocity, acceleration, force)
  • Null Vector (Zero Vectors):- It is a vector having zero magnitude and an arbitrary direction.
    When a null vector is added or subtracted from a given vector the resultant vector is same as the given vector.
    Dot product of a null vector with any arbitrary is always zero. Cross product of a null vector with any other vector is also a null vector.
  • Collinear vector:- Vectors having a common line of action are called collinear vector. There are two types.
    Parallel vector (θ=0°):- Two vectors acting along same direction are called parallel vectors.
    Anti parallel vector (θ=180°):-Two vectors which are directed in opposite directions are called anti-parallel vectors.
  • Co-planar vectors- Vectors situated in one plane, irrespective of their directions, are known as co-planar vectors.
  • Vector addition:-
    Vector addition is commutative- Kinematics Class 11 Notes Physics
    Vector addition is associative-  Kinematics Class 11 Notes Physics
    Vector addition is distributive-  Kinematics Class 11 Notes Physics
  • Triangles Law of Vector addition:- If two vectors are represented by two sides of a triangle, taken in the same order, then their resultant in represented by the third side of the triangle taken in opposite order.
    Kinematics Class 11 Notes Physics
    Magnitude of resultant vector Kinematics Class 11 Notes Physics
    R=√(A2+B2+2ABcosθ)
    Kinematics Class 11 Notes Physics
    Here θ is the angle between Kinematics Class 11 Notes Physics and Kinematics Class 11 Notes Physics
    If β is the angle between Kinematics Class 11 Notes Physics and  Kinematics Class 11 Notes Physics
    then,
    Kinematics Class 11 Notes Physics
  • If three vectors acting simultaneously on a particle can be represented by the three sides of a triangle taken in the same order, then the particle will remain in equilibrium.
    So, Kinematics Class 11 Notes Physics
  • Parallelogram law of vector addition:-
    Kinematics Class 11 Notes Physics
    Kinematics Class 11 Notes Physics
    Cases 1:- When, θ = 0°, then,
    R = A+B (maximum), β = 0°
    Cases 2:- When, θ = 180°, then,
    R= A-B (minimum), β = 0°
    Cases 3:- When, θ = 90°, then,
    R = √(A2+B2), β = tan-1 (B/A)
  • The process of subtracting one vector from another is equivalent to adding, vectorially, the negative of the vector to be subtracted.
    So, Kinematics Class 11 Notes Physics
  • Resolution of vector in a plane:-
    Kinematics Class 11 Notes Physics
  • Product of two vectors:-
    (a) Dot product or scalar product:-
    Kinematics Class 11 Notes Physics
    Here A is the magnitude of  Kinematics Class 11 Notes PhysicsB is the magnitude of Kinematics Class 11 Notes Physicsand θ  is the angle betweenKinematics Class 11 Notes Physics
    (i) Perpendicular vector:-
    Kinematics Class 11 Notes Physics
    (ii) Collinear vector:-
    When, Parallel vector (θ = 0°), Kinematics Class 11 Notes Physics
    When, Anti parallel vector (θ = 180°), Kinematics Class 11 Notes Physics
    (b) Cross product or Vector product:-
    Kinematics Class 11 Notes Physics
    Here A is the magnitude of Kinematics Class 11 Notes Physics , B is the magnitude of Kinematics Class 11 Notes Physics is the angle betweenKinematics Class 11 Notes Physicsand Kinematics Class 11 Notes Physics and Kinematics Class 11 Notes Physics is the unit vector in a direction perpendicular to the plane containing Kinematics Class 11 Notes Physics
    (i) Perpendicular vector (θ = 90°):-
    Kinematics Class 11 Notes Physics
    (ii) Collinear vector:-
    When, Parallel vector (θ = 0°), Kinematics Class 11 Notes Physics (null vector)
    When, θ = 180°,  Kinematics Class 11 Notes Physics (null vector)
  • Unit Vector:- Unit vector of any vector is a vector having a unit magnitude, drawn in the direction of the given vector.
    In three dimension,
    Kinematics Class 11 Notes Physics
  • Area:-
    Area of triangle:-  Kinematics Class 11 Notes Physics
    Area of parallelogram:-  Kinematics Class 11 Notes Physics
    Volume of parallelepiped:-  Kinematics Class 11 Notes Physics
  • Equation of Motion in an Inclined Plane:
    (i) Perpendicular vector :-  At the top of the inclined plane (t = 0, u = 0 and a = g sinq ), the equation of motion will be,
    (a) v= (g sinθ)t                                                          
    (b) s = ½ (g sinθ) t2
    (c) v2 = 2(g sinθ)s    
    Kinematics Class 11 Notes Physics
  • (ii) If time taken by the body to reach the bottom is t, then   s = ½ (g sinθ) t2
    t = √(2s/g sinθ)
    But sinθ =h/s   or s= h/sinθ
    So, t =(1/sinθ) √(2h/g)
    (iii) The velocity of the body at the bottom
    v = g(sinθ)t
    =√2gh
  • The relative velocity of object A with respect to object B is given by
    VAB = VA-VB
    Here, VB is called reference object velocity.
  • Variation of mass:- In accordance to Einstein’s mass-variation formula, the relativistic mass of body is defined as,
    m= m0/√(1-v2/c2)
    Here, m0 is the rest mass of the body, v is the speed of the body and c is the speed of light.
  • Projectile motion in a plane:- If a particle having initial speed u is projected at an angle θ (angle of projection) with x-axis, then,
    Kinematics Class 11 Notes Physics
    Time of Flight, T = (2u sinα)/g
    Horizontal Range, R = u2sin2α/g
    Maximum Height, H = u2sin2α/2g
    Equation of trajectory, y = xtanα-(gx2/2u2cos2α)
  • Motion of a ball:-
    (a) When dropped:-  Time period, t = √(2h/g) and speed, v = √(2gh
    (b) When thrown up:- Time period, t = u/g and height, h = u2/2g
  • Condition of equilibrium:-
    Kinematics Class 11 Notes Physics
The document Kinematics Class 11 Notes Physics is a part of the NEET Course NCERT Exemplar & Revision Notes for NEET.
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FAQs on Kinematics Class 11 Notes Physics

1. What is kinematics?
Ans. Kinematics is the branch of physics that studies the motion of objects without considering the forces causing the motion. It focuses on concepts such as displacement, velocity, and acceleration.
2. How is displacement different from distance?
Ans. Displacement refers to the change in position of an object from its initial position to its final position, taking into account both the distance and direction. On the other hand, distance is the total length covered by an object irrespective of its direction.
3. What is the difference between speed and velocity?
Ans. Speed is a scalar quantity that refers to how fast an object is moving, while velocity is a vector quantity that includes both the speed and direction of the object's motion. In other words, velocity specifies both the magnitude and the direction of the object's speed.
4. How is average velocity calculated?
Ans. Average velocity is calculated by dividing the total displacement of an object by the total time taken. It is a vector quantity that indicates the change in position per unit of time.
5. What is the difference between uniform and non-uniform motion?
Ans. Uniform motion refers to the motion of an object at a constant speed, where the object covers equal distances in equal intervals of time. Non-uniform motion, on the other hand, refers to the motion of an object at varying speeds, where the object covers unequal distances in equal intervals of time.
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