kinematics

• kinematics is the branch of physics concerned with the motion of objects without reference to the forces that cause the motion
• kinematics is the way we predict different parts of the motion only using other parts of the motion, without needing to know the nature of the object or the forces that act on it
• the motion of bodies through space and time can be described and analysed in terms of position, velocity and acceleration
• displacement is the change of position
• velocity is the rate of change of position
• acceleration is the rate of change of velocity
• a change in direction cause acceleration because:

  • acceleration is the change in velocity over time
  • velocity is the displacement over time
  • a change in direction changes the displacement, hence changing the velocity, hence causing a change in velocity over a certain time period (acceleration)
• instantaneous measures are measured at any given time, whereas average measures are averaged over a period of time
• steps to solving a kinematics problem:

  1. define one direction as being positive and the other as being negative
  2. kinematics can only be used if the acceleration is constant over the motion they are predicting - if there is more than one acceleration, split the problem up into multiple problems (one for each acceleration)
  3. solve for the missing value using the equations
• projectile: a particle moving freely, non-powered, under gravity, in a two dimensional plane
• an object is sent into a projectile motion trajectory with a resultant velocity at an angle to the horizontal
• for typical projectile motion, the time to the maximum height is half the total time
• in projectile motion, at the maximum height, the vertical velocity component is 0
• in projectile motion, the horizontal velocity component component is constant and therefore the horizontal acceleration is zero