EDU2MP Movement Perspectives

Linear Motion

• Movement in a straight line of a body or body part. (Translatory motion)

• The sprinter runs from A to B.

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Curvilinear Motion

• Movement along a curved line.

• Most jumps are along a curved line.

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Projectile Motion

• Motion of an object or person in flight.

EDU2MP Movement Perspectives

Linear Motion I – Middle SecondaryIntroduction to Linear Motion

speeddistance / displacement

velocityacceleration

Graphical representationdistance - time graphsspeed - time graphs

velocity - graphsLinear Motion II – Senior Secondary

Non-uniform motiondisplacement

velocityacceleration

instantaneous speedaverage speed

Uniform motionequations for uniform motion

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

Many sports involve the throwing of a ball or other object. This article discusses the

basics of projectile motion, and for ease of understanding, we will consider that there is no air resistance. The influence of air

resistance, friction, spin, and air flow around the object is discussed elsewhere Any projectile thrown, such as a ball, can

be considered to have a vertical and horizontal velocity component, as shown in

this diagram (blue=horizontal velocity component, red=vertical velocity

component). Throughout the path of the projectile,

change occurs only in the vertical direction due to the influence of gravity, while the horizontal component of the velocity will not change. (This is not quite true, there

will be a very small slowdown in the horizontal direction due to air resistance).

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Projectile Motion

EDU2MP Movement Perspectives

There are many examples of projectile motion is sport.

•Golf ball

•Basketballs

•Javelin

•Ski jumping

•Diving

•Trampoline

•Archery

•Soccer

•Football

•Cricket

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

The following factors influence the projectiles trajectory

Angle of release

Speed of release

Height of release

Gravity

Spin

Air resistance

See java demo

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Spin Magnus Effect

When sports players produce curve balls, be it through throwing, kicking or hitting a ball, they are exploiting the Magnus effect.

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The Magnus effect causes a spinning ball moving through air (or any other fluid such as water) to produce a force perpendicular to both its spin axis and its direction of travel. This force causes the ball to curve either left or right if the spin axis is vertical. If the spin axis is both horizontal and perpendicular to its direction of travel then the ball will either descend faster or slower than it would otherwise under the influence of gravity alone.

Magnus Effect is a lifting force produced when a rotating cylinder produces a pressure differential. This is the same effect that makes a baseball curve or a golf ball slice.

The difference in surface velocity accounts for a differ-ence in pressure, with the pressure being lower on the top than the bottom. This low pressure area produces an upward force known as the “Magnus Effect.” This mechanically induced circulation illustrates the rela-tionship between circulation and lift.

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Friction

FrictionFriction can be defined as the resistance to motion of two moving

objects or surfaces that touch.

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COR

To find the coefficient of restitution in the case of a falling object bouncing off the floor, or off a racquet on the floor, use the following formula:

                  

c = coefficient of restitution (dimensionless)h = bounce heightH = drop height

The coefficient of restitution (denoted by the symbol c in our formulas) is a measure of the elasticity of the collision between ball and racquet.

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And the coefficient of restitution merely tells you how much of the original kinetic energy remains after a collision of the clubhead with the golf ball.  

The higher the coefficient of restitution, the faster the ball will be propelled by the clubhead for a given impact speed.  

So why all the fuss over this figure?  

It's because the USGA is trying its best to limit the influence of technology in golf. Theory being that golf should challenge the skill and savvy of the individual rather than the technology in his or her bag. And this is probably a good thing for the sport. After all, it would be very effective to go bass fishing by dropping depth charges over the side of your boat. Just scoop 'em up when they float to the surface. But would that really be bass fishing?

 

So the USGA has adopted limits of 0.830 on the coefficient of restitution a given clubface may have as part of its effort to define the boundaries of technology in the game.

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

Projectile Motion

• Motion of an object or person in flight.

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Factors Affecting Pathways

The pathway of an object is determined by:

• The angle of release.

• Drag force is a resistant force

• Lift force

• Type of spin

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

• When an athlete launches himself or an object into flight gravity will act as a force pulling the athlete or object towards the ground. The flight path of the centre of gravity of a body is a curve called a parabola. The parabolic flight path depends on three factors:

• ● Speed of take off or release • ● Angle of take off or release • ● Height of the athlete's CG at take off, or CG of implement at

release•     Of these, the speed of an athlete at take off, or of an implement at

release, is the most important factor. Greater speed means greater distance achieved. Air resistance can also affect the distance travelled by an athlete or implement.

•  

EDU2MP Movement Perspectives

EDU2MP Movement Perspectives

Drag Force

• Drag force is a resistance force - a force that slows the motion of a body through a fluid (air or water).

• Sportsmen reduce drag by using specialised techniques, equipment or clothing.

• Streamlining reduces form drag.

"Photos courtesy of and copyright Free Range Stock, www.freerangestock.com"

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Lift Force

• Lift force is a force generated perpendicular to fluid flow.

Direction of fluid

flow

Lift force

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Types of Spin

• Spin is the rotation of a body or object.• Torque is the force which creates spin.• The type and amount of spin depends on how

much torque is applied and where it is applied.

TOPSPIN

BACKSPIN

SIDESPIN

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Outcome of Spin

• Players learn to control the amount of spin to achieve different effects.

• Draw diagrams to represent the outcome the different types of spin.