Download APPLICATION OF FORCES

APPLICATION OF FORCES
IMPULSE
• Quite simply the time it takes a force to be
applied to an object or body and is often
related to a change in momentum.
• In sport, impulse can be used to add speed to
a body or object, or slow them down on
impact.
• Impulse = Force x Time
• When we run, our foot lands on the ground.
This is called FOOTFALL.
IMPULSE (cont.)
• When our foot hits the ground, our muscles
contract, force is applied to the ground, the
ground reaction force acts on the foot and the
force is transmitted to the rest of the body.
• We then move forward to the next footfall.
INTERPRETING FORCE – TIME GRAPHS
• Negative Impulse – a force generated when
absorbing body motion – landing
• Positive Impulse – an impulse that moves the
body
FORCE – TIME GRAPHS
• Page 110 – 111
• Draw fig 8.2 – write the heading
• Using the example of a sprinter, draw the
other 3 graphs of the different stages of the
race.
• Write a note under each graph explaining why
there is a NET positive, zero or negative
impulse and WHY this is.
FLIGHT PATHS OF OBJECTS IN SPORT
• projectile motion – factors affecting
distance,
• vector components of parabolic flight
WHY ARE WE INTERESTED IN IT??!
• The flight path of an object helps determine
the optimal angle of release. By finding this,
the performer will help maximise the distance
thrown.
• We will use the example of throwing the
shot……..
A PARABOLIC CURVE
• Copy figure 8.10 p.116
• UNDERSTAND the following:
• Horizontal Component: the horizontal motion
of an object in a parabolic flight curve
• Vertical Component: the upward motion of an
object in a parabolic flight curve
• Gravity constantly pulling the shot towards
the Earth
WHAT AFFECTS THE DISTANCE
THROWN?
•
•
•
•
Height of release
Speed of release
Angle of release
Air resistance (not so much in the shot, but
really important in e.g the discus)
• The weight of the object thrown – lighter
objects e.g shuttlecocks, are affected more by
air resistance
THE LAST BIT!!!!!!!!!!!!
• angular motion – conservation of angular
• momentum during flight, moment of inertia
• and its relationship with angular velocity.
ANGULAR MOTION / MOVEMENT
• ‘the movement of a body or mass around an
axis – spinning, rotating, turning’.
• Angular momentum is the amount of motion
a body has when rotating.It is not the speed. It
is the product of ANGULAR VELOCITY and THE
MOMENT OF INERTIA.
• Angular Momentum = Angular Velocity x
Moment of Inertia
COME ON!!!!
• M.O.I – resistance of a body to a change of
state when rotating
• Angular Velocity – the rate of movement in
rotation (its speed)
• Newton’s 1st Law of Angular Motion:
• ‘a rotating body will continue to turn about its
axis with constant angular momentum unless
an external force acts upon it.
THE LAST EVER SLIDE!
• This is also called ‘CONSERVATION OF ANGULAR
MOMENTUM’.
• The forces that might act on a rotating body are
air resistance or friction.
• ICE SKATING example in revision pack…
• Skaters spin on the ice with arms out = SLOW spin
as air resistance acts on arms
• Bring their arms into ‘streamline position’ =
FASTER spin as less air resistance
• This is because the MOI has changed resulting in
greater angular velocity
ARMS OUT = SLOW
ARMS IN = FAST