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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•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


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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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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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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





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)



•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%!


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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


4. GRAVITY4. GRAVITY

GRAVITY– Downwards force brings projectile back to the ground (“what

comes up, must come down”)


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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6. EFFECT OF SPIN ON TRAJECTORY OF BALL6. EFFECT OF SPIN ON TRAJECTORY OF BALL

TOP SPIN

BACK SPIN

NO SPIN

DISTANCE (m)18

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

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