# 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 1 st 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