Physics: Kinematics

Physics: Kinematics

1. Definition of terms

   • Distance: a physical unit that describes how far an object is or describes the length an object has covered during its motion. (scalar quantity)
   • Displacement: the distance travelled along a specified direction. (vector quantity)
   • Speed: the distance moved per unit of time taken. (scalar quantity)
     • Average speed: total distance / total time taken
   • Velocity: the rate of change of displacement (vector quantity)
     • Average velocity: total displacement moved / total time taken
   • Acceleration: rate of change of velocity (vector quantity)
     • An object that has an equal increase in velocity per unit of time has constant/uniform acceleration.

2. A scalar quantity only has magnitude

3. A vector quantity has magnitude and direction.

4. Kinematics equations

   • are used in situations in which the object has uniform acceleration and is travelling in a straight line. (one-dimensional motion/ rectilinear motion)
   • v = u + at
   • s = 1/2(v+u)t
   • s = ut + 1/2at^t
   • s = vt - 1/2at^2
   • v^2 = u^2 + 2as
   • where: v=final velocity, u=initial velocity, s=displacement, a=acceleration, t=time

5. Projectile motion (two-dimensional motion)

   • for displacement calculation, use the kinematic equation--s = ut + 1/2at^2
     • x-axis displacement: s = ut (no acceleration in horizontal motion)
     • y-axis displacement: s = 1/2gt^2
   • for velocity calculation, use the kinematic equation--v = u + at
     • x-axis velocity: v = u
     • y-axis velocity: v = gt
       • At maximum height, the velocity of the y-axis is 0.
   • for resultant velocity, use the Pythagoras Theorem
     • to find the angle of resultant velocity (between the horizontal velocity and resultant forces), use trigonometry (tan__(tither) = Vy/Vx