Projectile Motion Flashcards

Biomechanics

Projectile Motion

• Definition: A body released into the air becomes a projectile.
• Examples: Throwing (discus, softball, lacrosse), striking (tennis, football, cricket), projecting the body (diving, jumping, gymnastics).
• Trajectory: The path a body follows through the air, typically parabolic.

Syllabus Dot Points

• Application of projectile motion to sport in relation to:
  • Optimal projection
  • Parabolic trajectory
  • Release of projectiles angle

Factors Affecting Projectile Motion/Optimal Projection

• Velocity of release
• Angle of release
• Height of release

Components of Projectile Motion

• Combines horizontal and vertical motion/velocity.
• Gravity acts to change the motion of the projectile.

Horizontal Component (Motion/Velocity)

• Acts parallel to the ground.
• No tendency to lift the object into the air.
• Horizontal Velocity: The distance and the rate of movement at which the body/projectile is going out/across.
• Projectiles maintain the same horizontal velocity throughout its flight. Only air resistance and gravity will change its state of motion.

Vertical Component (Motion/Velocity)

• Vertical Velocity: The rate of movement of which the body is going up.
• Vertical velocity determines the height of the apex, affecting the height the projectile reaches and the time it takes to reach it and return to the landing point.
• Vertical Velocity is imparted on the body at the time of release/takeoff and is responsible for the lifting of the body into the air.
• Vertical height and the time of the flight are determined by the vertical velocity at release/take-off.
• Time in flight = time taken for the body to reach its peak (trajectory up) + time taken for it to land (trajectory down).
• The two components (vertical and horizontal) can be varied to maximize our needs.

Take-off Velocity, Angle, and Height of Center of Gravity (C of G)

• All related to the skill being analyzed.
• Horizontal displacement increases with take-off velocity, and theoretically, a take-off angle of 45° produces the greatest distance.
• However, in the long jump, take-off angles are approximately 20° as athletes cannot jump at 45° and still retain a high horizontal running velocity (horizontal emphasis).
• An emphasis on vertical displacement requires an increase in the take-off angle (approximately 60° greater vertical velocity compared with long jump) with a reduction in the approach horizontal velocity.
• Height of take-off must be considered for both sporting actions with an emphasis on horizontal or vertical displacement; consider the position of the center of gravity at take-off.

Optimal Projection

• The path of the body or an object in flight is predetermined at the moment of take-off by 3 factors:
  1. Velocity at release/take-off
  2. Angle of release/take-off
  3. Height of release/take-off (compared to landing)
• Velocity at release/take-off has the greatest influence. It will determine height (vertical) and length (horizontal) of the trajectory (when all other factors are constant).
• The greater the initial vertical velocity, the greater the flight time and the greater the height reached.
• The greater the initial horizontal velocity, the greater the horizontal distance.
• In many sports, the speed of the body/projectile is more important than gaining maximum distance (i.e., basketball or softball).

Height of Release (Compared to Landing) and its Influence on the Angle of Release

1. The projectile is released and lands at the same level:
   • The optimum angle of release is 45°.
2. The projectile is released from a higher position than the landing point:
   • The optimum angle of release is less than 45° (e.g., shot put).
3. The projectile is released from a lower position than the landing point:
   • The optimum angle of release is greater than 45° (e.g., basketball).

Angle of Release/Take-off

• Long Jumpers: can have a release angle of 22° as they are aiming for maximum horizontal distance. If they were to take off at 45° they would have to slow down to be able to accelerate upwards therefore, decreasing their horizontal velocity gained on the run up.
• The lower the angle of release the faster the projectile will reach its destination
• However, if the release angle is too low, the vertical component will be reduced thus reducing the time of flight which in turn reduces the horizontal distance i.e. the projectile will hit the landing point before reaching the target

Tasks: Manipulating the Three Features of a Projectile

• Shoot an elastic band using different launch angles to evaluate distance traveled. How does the angle of release influence distance?
• If you use different strength/width bands does this influence distance traveled for the same angle?

Determining the Optimal Angle of Release

• Evaluate the role of the angle of release on horizontal displacement.
• Working in pairs, ask your partner to throw a shuttlecock at a 45° angle at maximum velocity, such that you are able to catch the shuttle at a similar height to the release height.
• Draw and label the flight path/trajectory of a 45° angle of release on a piece of graph paper.
• Determine the optimal angle of release for the shuttlecock.
• Throw above an angle of 45° then draw and discuss the shape of the flight path.
• Throw below an angle of 45° then draw and discuss the shape of the flight path.

What impact does an increase in the angle of release have on:

• The horizontal displacement of the shuttle?
• The vertical displacement of the shuttle?