Physics (9702)
Topic 1 of 1Cambridge A Levels

Kinematics

Describing motion with equations and graphs

A-Level kinematics builds on O-Level speed/distance/time with more sophisticated equations and vector analysis.


SUVAT Equations (for constant acceleration):

  • v = u + at
  • s = ut + ½at²
  • v² = u² + 2as
  • s = ½(u + v)t

    • Where: s = displacement, u = initial velocity, v = final velocity, a = acceleration, t = time


    Vectors vs Scalars:

  • Scalar: magnitude only (speed, distance, mass, energy)
  • Vector: magnitude AND direction (velocity, displacement, force, acceleration)

    • Projectile Motion:

    An object launched at an angle follows a parabolic path. Split motion into:

  • Horizontal: constant velocity (no air resistance assumed)
  • Vertical: constant acceleration due to gravity (g = 9.81 m/s²)
  • These components are independent of each other!

    • Free Fall:

  • Object falling under gravity only
  • Acceleration = g = 9.81 m/s² (downward)
  • At the top of trajectory, vertical velocity = 0 (but horizontal velocity continues)

    • Key Points to Remember

    • 1SUVAT: v=u+at, s=ut+½at², v²=u²+2as
    • 2Vectors have magnitude AND direction, scalars only magnitude
    • 3Projectile motion: horizontal and vertical components are independent
    • 4g = 9.81 m/s² (acceleration due to gravity)

    Pakistan Example

    Shaheen Afridi's Bowling — Projectile Motion

    When Shaheen Afridi releases a ball at 150 km/h (41.7 m/s) at an angle of 10° below horizontal from a height of 2.2m: Horizontal velocity = 41.7cos10° = 41.1 m/s (stays constant). Vertical initial velocity = 41.7sin10° = 7.24 m/s downward. Using s = ut + ½gt², we can calculate exactly when and where the ball bounces on the pitch. The pitch is ~20m away, so time = 20/41.1 = 0.49s. This is real physics happening every ball in a cricket match!

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