Projectile Motion

• Projectile

  a body launched into the air which is subject to weight & air resistance
• Projectile Motion

  the movement of a body through the air following a curved flight path under the force of gravity
• Factors Affecting Horizontal Distance of a Projectile

  • speed of release
  • angle of release
  • height of release
  • aerodynamic factors
• Speed of Release

  • biggest effect on horizontal distance
  • increased velocity of release increases horizontal distance travelled
  • Newtons second law of motion - the greater the force applied to the projectile, the greater the change in momentum & therefore acceleration of the projectile into the air

  e.g speed of rotation of hammer throw
• Angle of Release

  • release at 90 - projectile will accelerate vertically upwards & come straight back down
  • release at 45 - optimal angle to maximise horizontal distance
  • release at >45 - projectile reaches peak height too quickly & rapidly returns to ground
  • release at <45 - projectile doesn't achieve sufficient height to maximise flight time
• Height of Release

  • the higher the release, the further the horizontal distance travelled

  e.g height of javelin throwers/ shotput throwers
• Projectiles in Flight

  • once a projectile has left the ground, there are only 2 forces acting on it (weight & air resistance)

  Factors Affecting Projectile in Flight:

  velocity

  frontal cross-section area

  mass of the body
• Parabola

  a uniform curve symmetrical about its highest point
• Parabolic Flight Path

  a flight path symmetrical about its highest point caused by the dominant weight force of a projectile

  e.g shot putt
• Non-Parabolic Flight Path

  a flight path asymmetrical about its highest point caused by the dominant force of air resistance on the projectile

  e.g shuttle cock, discus
• Projectiles in Flight Diagram

  ..

  
• Free Body Diagrams

  • weight & air resistance should originate from the CoM of the projectile
  • weight should project downwards
  • air resistance should project opposite the direction of motion
  • always include a direction of motion arrow

  
• Parallelogram of Forces

  • considers the result of all forces acting on the projectile
  • resultant force shows the acceleration of a projectile & the direction in which it accelerates
  • if W>AR the flight path is parabolic
  • if AR>W the flight path is non-parabolic