Physics Lens

02. Kinematics

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[accordion title=”1. Definitions”]

  • Displacement is the distance travelled along a specified direction.
  • Speed is the rate of change of distance travelled.
  • Velocity is the rate of change of displacement.
  • Acceleration is the rate of change of velocity.


[accordion title=”2. One-Dimensional Motion with Constant Acceleration”]

  • $$v=u+at$$
  • $$s=(\frac{u+v}{2})t$$
  • $$s=ut+\frac{1}{2}at^2$$
  • $$v^2=u^2+2as$$

s: displacement
u: initial velocity
v: final velocity
a: acceleration
t: time


[accordion title=”3. Two-Dimensional Motion”]

  • Tip: Sometimes, you will require two equations to solve a kinematics problem. For a parabolic path in a projectile motion without resistive forces, you can draw a table such as the one below and fill in the blank with the information given in the question.
Initial velocity at an angle
Initial velocity at an angle
  • In the case where a projectile is launched at an angle $$\theta$$ to the horizontal and undergoes the acceleration of free fall, the various horizontal and vertical components of displacement, velocity and acceleration can be expressed in the following way:
Horizontal Vertical
displacement, s $$(u \cos \theta)t$$ $$(u \sin \theta)t+\frac{1}{2}gt^2$$
initial velocity, u $$u \cos \theta$$ $$u \sin \theta$$
initial velocity, v $$u \cos \theta$$ $$u \sin \theta +gt$$
acceleration, a 0 $$g$$
time, t same for both dimensions