2A/2B BIOMECHANICS 2 nd ed. 1 ©PE STUDIES REVISION SEMINARS.
Transcript of 2A/2B BIOMECHANICS 2 nd ed. 1 ©PE STUDIES REVISION SEMINARS.
2A/2B BIOMECHANICS 2nd ed.2A/2B BIOMECHANICS 2nd ed.
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PROJECTILE MOTIONPROJECTILE 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”
• “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”
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Curriculum Council of Western Australia. Physical Education Studies Support Document 2009.
WHAT IS A PROJECTILE?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”)
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TRAJECTORY OF A PROJECTILE – FORCE MOTIONTRAJECTORY 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
curve1. Horizontal 2. Vertical
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
When the landing height and release height are equal, the trajectory of a projectile forms a
smooth symmetrical curve known as a PARABOLA
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FACTORS AFFECTING FLIGHT OF PROJECTILEFACTORS AFFECTING FLIGHT OF PROJECTILE
The flight path of a projectile is determined by:1. Its angle of release2. Its height of release3. Its speed of release4. Gravity5. Air resistance6. Spin
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1. ANGLE OF RELEASE1. 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!)
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• If all other factors are constant (i.e. Speed of release, height of release, spin, air resistance);
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1. ANGLE OF RELEASE1. ANGLE OF RELEASE
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•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
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HORIZONTAL MOTION
1. ANGLE OF RELEASE1. ANGLE OF RELEASE
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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 RELEASE2. 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.
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2. HEIGHT OF RELEASE2. HEIGHT OF RELEASE
HORIZONTAL COMPONENTHORIZONTAL COMPONENT
Landing heightLanding height
Optimal angle of release is =45⁰
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
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
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2. HEIGHT OF RELEASE2. HEIGHT OF RELEASE
HORIZONTAL COMPONENTHORIZONTAL COMPONENT
Landing heightLanding height
Optimal angle of release is >45⁰
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
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
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2. HEIGHT OF RELEASE2. HEIGHT OF RELEASE
HORIZONTAL COMPONENTHORIZONTAL COMPONENT
Landing heightLanding height
Optimal angle of release is <45⁰
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
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
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GENERAL PRINCIPLES– Release height=landing height = 45° (Kicking soccer ball from ground)– Release height>landing height<45° (Throwing)– Release height<landing height>45° (Hitting golf ball onto elevated green)
2. HEIGHT OF RELEASE2. HEIGHT OF RELEASE
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•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 RELEASE2. HEIGHT OF RELEASE
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3. VELOCITY AT TAKE OFF3. 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
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4. GRAVITY4. GRAVITY
GRAVITY– Downwards force brings projectile back to the ground (“what
comes up, must come down”)
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5. EFFECT OF AIR RESISTANCE ON BATTED BASEBALL
5. EFFECT OF AIR RESISTANCE ON BATTED BASEBALL
TAIL WIND
HEAD WIND
NO WIND
40m 80m 120m
DISTANCE (m) 17
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