Transcript Projectile Motion

Biomechanics
• Mechanics of movement:
– vectors and scalars – velocity, acceleration and
momentum/impulse in sprinting
– Newton’s Laws applied to movements –
application of forces in sporting activities
– projectile motion – factors affecting distance,
vector components of parabolic flight
– angular motion – conservation of angular
momentum during flight, moment of inertia
and its relationship with angular velocity.
Newton’s Laws
Whiteboards-
1. What is Newton’s 1st Law?
2.What is Newton’s 2nd Law?
3.What is Newton’s 3rd Law?
4.Use Newton’s Laws to explain the
movement of a sprinter from the start
of the race in the blocks, until half way
through the race.
Projectile Motion
Projectile Motion is the study of the motion of
objects moving through the air, such as a rugby
ball, shuttlecock or shot put.
Understanding projectile motion can help
athletes and coaches optimise performance
through maximising the distance or accuracy
with which they can be thrown or kicked, or
anticipating where an object will land.
Pgs 88-89
Projectile Motion
The flight of an object depends on the following:
• The size of the action / driving force
• The mass of the object
• Air resistance
• Gravity
These two
determine the
acceleration
of the object
– why?
Once an object has left the hand / foot / racket of the
athlete, the action force remains constant.
Gravity and the weight of the object also remain constant.
Therefore the overriding factor determining an object’s
flight path is the air resistance.
Recap - Air Resistance
When a body or object moves through air (or
water) it is subject to fluid friction, which acts
in the opposite direction to the motion of the
moving body.
The amount of air resistance depends upon:
• The Shape of the object
• The Size of the object
• The Speed of the object
Flight Paths
Air resistance offered to a projectile whilst in
motion may change the parabolic flight path.
Flight paths can be categorised in two ways:
• Parabolic (symmetrical) – this is where the
air resistance on an object is negligible so
there is no force counteracting the action
force
• Distorted Parabolic (asymmetrical) – this is
where the air resistance is large, taking the
object away from the normal parabolic flight.
Flight Paths
Shot Put Flight
Since air resistance is governed by…
the size, shape and speed of an object…
… shot put flight is not significantly affected by
air resistance.
Why not?
In this case, it is the…
• Velocity of release
• Height of release
• Angle of release
that will be the factors that determines the
shot put’s flight path.
Shot Put Flight
The initial velocity that any object has can be divided into two
components – the horizontal component and the vertical component.
Vertical
Component
Horizontal
component
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Rules for drawing shot put flight
There are some simple rules that will help you gain full
marks on the shot put exam question:
1. The horizontal component remains constant because
there is no air resistance
2. The vertical component starts off large, but is zero at
the apex (top) of the flight path
3. The vertical component becomes negative after the
apex due to gravity
4. The final vertical component is larger than (but
opposite to) the initial vertical component
5. The shot put path ends lower than it started – thrown
from head height, lands on the ground!
Shot Put Flight
Since air resistance is governed by…
the size, shape and speed of an object…
… shot put flight is not significantly affected by
air resistance.
In this case, it is the…
• Velocity of release
• Height of release
• Angle of release
Use page 90-92 to
summarise how a shotputter would obtain the
optimal flight path, and why
each aspect is important
that will be the factors that determines the
shot put’s flight path.
Shuttlecock Flight
• Explain why the effects of air resistance are much
greater on a shuttlecock than on a shot put
• What effect does the air resistance have on the flight
of the shuttlecock? Explain your answer in terms of
horizontal and vertical velocity components
• Sketch the flight path of a shuttlecock. Add
approximate vectors for the horizontal and vertical
velocity components.