2A/2B BIOMECHANICS 2 nd ed. 1 ©PE STUDIES REVISION SEMINARS

PROJECTILE MOTION “Define and apply projectile motion to a selected sport in relation to the principle of optimal projection, parabolic trajectory, release of projectiles- angle, velocity and height” ©PE STUDIES REVISION SEMINARS 2 Home Curriculum Council of Western Australia. Physical Education Studies Support Document 2009.

WHAT IS A PROJECTILE? A projectile is an object propelled into the air or water by an external force. There are 2 naturally occurring forces acting on a projectile 1.AIR RESISTANCE – Important in ski jumping, skydiving – In discus, javelin, golf, air resistance affects the aerodynamic characteristics of the projectile. 2.GRAVITY – Downwards force brings projectile back to the ground (“what comes up, must come down”) 3©PE STUDIES REVISION SEMINARS Home

TRAJECTORY OF A PROJECTILE – FORCE MOTION The path of a projectile is referred to as its trajectory It has two components causing the trajectory of the projectile to curve 1.Horizontal 2.Vertical VERTICAL MOTION HORIZONTAL MOTION When the landing height and release height are equal, the trajectory of a projectile forms a smooth symmetrical curve known as a PARABOLA 4 ©PE STUDIES REVISION SEMINARS Home

FACTORS AFFECTING FLIGHT OF PROJECTILE The flight path of a projectile is determined by: 1.Its angle of release 2.Its height of release 3.Its speed of release 4.Gravity 5.Air resistance 6.Spin 5 ©PE STUDIES REVISION SEMINARS Home

1.ANGLE OF RELEASE The angle of release of a projectile determines trajectory shape. With all other things held constant it also determines: – The time the object stays in the air – The horizontal distance the object moves. Theoretical optimal angle of release for distance = 45⁰ provided height of release and landing height remain equal and spin and air resistance are not present (this of course never occurs on earth!) 6 ©PE STUDIES REVISION SEMINARS Home

If all other factors are constant (i.e. Speed of release, height of release, spin, air resistance); ©PE STUDIES REVISION SEMINARS7 1.ANGLE OF RELEASE Home An angle of less than 45⁰ results in shorter horizontal distances, shorter vertical distances and shorter flight times This might be useful in the following sports; Throwing in softball, cricket etc, stab pass in AFL An angle of less than 45⁰ results in shorter horizontal distances, shorter vertical distances and shorter flight times This might be useful in the following sports; Throwing in softball, cricket etc, stab pass in AFL An angle of greater than 45⁰ results in shorter horizontal distances, greater vertical distances and longer flight times. This might be useful in the following sports; High Jump, Pole Vault, punting in American Football An angle of greater than 45⁰ results in shorter horizontal distances, greater vertical distances and longer flight times. This might be useful in the following sports; High Jump, Pole Vault, punting in American Football

©PE STUDIES REVISION SEMINARS8 VERTICAL MOTION HORIZONTAL MOTION 1.ANGLE OF RELEASE Home Angle of release = 45⁰ Vertical and horizontal velocity is equal Max horizontal distance attained Angle of release = 45⁰ Vertical and horizontal velocity is equal Max horizontal distance attained Angle of release > 45⁰ Vertical velocity is greater than horizontal ↑ height and flight time ↓horizontal distance Angle of release > 45⁰ Vertical velocity is greater than horizontal ↑ height and flight time ↓horizontal distance Angle of release < 45⁰ Horizontal velocity is greater than vertical ↓ height and flight time ↓horizontal distance Angle of release < 45⁰ Horizontal velocity is greater than vertical ↓ height and flight time ↓horizontal distance

2.HEIGHT OF RELEASE Many sports involve projecting a ball from a given height & the ball then landing at ground level. The greater the height of release of a projectile, the greater the horizontal distance it will cover, provided all other factors are equal ©PE STUDIES REVISION SEMINARS Home

2.HEIGHT OF RELEASE VERTICAL COMPOENT HORIZONTAL COMPONENT Release height Landing height Optimal angle of release is =45⁰ When the projectile is released from the same level at which it lands, the time for the projectile to reach its peak equals the time it takes to land 10 ©PE STUDIES REVISION SEMINARS Home

2.HEIGHT OF RELEASE VERTICAL COMPOENT HORIZONTAL COMPONENT Release height Landing height Optimal angle of release is >45⁰ When the projectile is released from a lower position at which it lands, the time for the projectile to reach its peak is greater than the time it takes to land 11 ©PE STUDIES REVISION SEMINARS Home

2.HEIGHT OF RELEASE VERTICAL COMPOENT HORIZONTAL COMPONENT Release height Landing height Optimal angle of release is <45⁰ When the projectile is released from a higher position than which it lands, the time for the projectile to reach its peak is less than the time it takes to land 12 ©PE STUDIES REVISION SEMINARS Home

GENERAL PRINCIPLES – Release height=landing height = 45° (Kicking soccer ball from ground) – Release height>landing height<45° (Throwing) – Release height 45° (Hitting golf ball onto elevated green) 2.HEIGHT OF RELEASE 13©PE STUDIES REVISION SEMINARS Home It must be noted an athlete must not sacrifice release speed for added release height or optimal theoretical angle of release. Constraint relationships among projection speed, height and angle – When one is shifted closer to what would theoretically be optimal, another moves farther away from being optimal – human anatomy dictates certain constraints It must be noted an athlete must not sacrifice release speed for added release height or optimal theoretical angle of release. Constraint relationships among projection speed, height and angle – When one is shifted closer to what would theoretically be optimal, another moves farther away from being optimal – human anatomy dictates certain constraints

E.g. During a long jump, because take off and landing heights are the same, theoretically optimum angle of take-off should be 45 . However, if we were to take off at this angle, long jumpers would decrease the horizontal velocity they could otherwise obtain by approximately 50%! 2.HEIGHT OF RELEASE 14 ©PE STUDIES REVISION SEMINARS Home

3.VELOCITY AT TAKE OFF The greater the speed or velocity of release, the greater the distance a projectile will carry. The speed of release is the most important factor when maximising the distance travelled. Velocity of projectile at instant of release will determine the height + length of the trajectory as long as all other factors held constant – Vertical velocity component determines height of apex – Horizontal component is constant throughout flight of projectile if air resistance =0 and is determined at point of release 15©PE STUDIES REVISION SEMINARS Home

4. GRAVITY GRAVITY – Downwards force brings projectile back to the ground (“what comes up, must come down”) 16©PE STUDIES REVISION SEMINARS Home

5.EFFECT OF AIR RESISTANCE ON BATTED BASEBALL TAIL WIND HEAD WIND NO WIND 40m80m120m DISTANCE (m) HEIGHT (m) 17 ©PE STUDIES REVISION SEMINARS Home

6. EFFECT OF SPIN ON TRAJECTORY OF BALL TOP SPIN BACK SPIN NO SPIN DISTANCE (m) HEIGHT (m) 18 ©PE STUDIES REVISION SEMINARS Home