Projectile motion

• Projectile motion 


  The movement of a body through the air following a curved flight path under the force of gravity.
• A projectile is a body launched into the air and subjected to weight and air resistance forces.
• Projectile release will affect the overall horizontal distance.
• 4 Key factors of projectile release


  1. Speed of release
  2. Angle of release
  3. Height of release
  4. Aerodynamics
• Speed of release 


  The greater the force applied to the body / projectile the greater the acceleration, therefore the further it will travel.
• Angle of release 


  The angle of release will affect the horizontal distance reached by a projectile.
• Angle of release 


  The angle of release will affect the horizontal distance reached by a projectile.

  
• Angle of release (AoR) - 90 degrees


  The projectile will accelerate vertically and come straight back down.
• AoR 45 degrees 


  Optimal angle to maximise horizontal distance
• AoR greater than 45 degrees 


  Projectile reaches peak to quickly.
• AoR less than 45 degrees


  Projectile does not achieve sufficient height to maximise flight time.
• Height of release 


  45 degrees is the optimal angle of release if release height and landing height are equal.
• Positive release height is if the release height is above the landing height , the optimum angle is lower as the projectile already has an increased flight time due to the increased height of release.
• Positive release height eg

  Javelin - optimum angle of release is less than 45 degrees as the projectile already has an increased flight time due to increased height of release.
• Negative release height is if the release height is below the landing height the optimum angle is higher.
• Negative release height eg 


  Golf bunker shot - needs greater angle of release to avoid the obstacle.
• Projectiles in flight 


  The flight path of a projectile unaffected by air resistance is known as parabola.
• Parabola 


  A uniform curve , symmetrical about its highest point.
• A projectile is affected by weight and air resistance.
• Depending on the dominant force , the flight path will be more or less parabolic in shape.
• Parabolic flight path

  A flight path symmetrical about its highest point caused by the predominant weight force of a projectile.

  
• Non - parabolic flight paths

  A flight path asymmetrical about its highest point caused by the dominant force of air resistance on the projectile.
• Flight paths

  A) Shuttle

  B) Discus

  C) non

  
• The forces acting on a projectile can be represented as a free body diagram.
• Free body diagrams show 


  • Which forces are acting
  • Where the forces originate
  • The relative sizes of the force
  • The direction of the force
• 3 phases of motion

  1. Start of flight
  2. Mid flight
  3. End of flight
• Over these phases...

  • Weight force does not change
  • Air resistance is dependent on projectile velocity
  • Air resistance is greater at the start of flight (high velocity)
  • Weight force becomes dominant at an objects highest point.
• Parallelogram of forces 


  If the resultant force line is closer to weight , weight is therefore dominant and the flight path is likely to be more parabolic.
• Mid flight free body diagrams

  A) Air resistance

  B) Weight

  C) Direction of motion

  D) Weight

  E) Parabolic

  F) Air resistance

  G) Weight

  H) Direction of motion

  I) Air resistance

  J) Non parabolic

  
• Parallelogram of forces 


  If the resultant force line is closer to air resistance, then air resistance is dominant and the flight path is likely to be more non parabolic.
• Parallelogram of forces

  A) Resultant force

  B) Resultant force