Motion
Vectors
Scalar quantities
 Speed, 100km/hr
Vector quantities
 100km/hr North or Force of gravity
 vectors are straight-line segments with one end defined as the
tail and the arrow tip defined as the head.
Adding Vectors

 Vectors can be added together using the head to tail method
 to add vector B to vector A, an identical vector is drawn (same
length and direction) as vector B beginning at the head of vector
A

Mass and Inertia
Mass is the measure of how much matter an object has
Centre of Mass:
 not located in the centre for objects that are not uniform
 app. 15cm above groin area
 slightly higher for males
Weight vs. Mass
Mass

 measured in kilograms (kg)
Weight

 measured in Newtons (N)

 (9.8 m/s2)

Inertia is the reluctance of an object to change its state of motion
from rest to moving, to moving faster, or to slowing down back to
rest
 Rotating objects have a reluctance to change their angular motion
Moment of inertia is a function of the mass of a rotating object and
how its mass is distributed about its axis of rotation
 The more massive an object, the greater its moment of inertia
Ex:
 The greater the distance of a rotating object from the centre of
rotation, the greater its moment of inertia
Ex:
Newton’s First Law of Motion
 An object will not change its state of motion (it will continue to
be at rest or moving with constant velocity), unless acted upon by
a net , external force
For example:
Newton’s Second Law of Motion
 For linear movements, the acceleration (a) a body experiences is
proportional to the force (F) causing it, and takes place in the
same direction as the force
 For angular movements, the angular acceleration of a body is
proportional to the moment of force causing it, and takes place in
the same direction as the moment of force
The greater the force
applied to a soccer ball
that has the same mass,
the greater the ball’s
acceleration
As the soccer ball’s mass
increases, it experiences
less acceleration from a
kick of the same force
As the mass of the
soccer ball is increased,
greater force must be
generated if the ball is to
have the same
acceleration
Impulse, Impact and Momentum
Momentum
Impulse
Impact
 Momentum is created by an impulse and is lost through impact
 Impulse and impact are both associated with bodies that are
changing their state of motion by experiencing large
accelerations over relative short time periods
 Collision or impact skills can sometimes manipulate the time of
contact and reduce the magnitude of the external force
 To increase impulse, a sprinter must increase the net external
force per step

 Gymnasts flex upon landing to allow greater time for external
forces of the floor to impact their bodies, thus decreasing force
Newton’s Third Law of Motion
 Every action has an equal and opposite reaction
 The two acting forces are equal in magnitude, but opposite in
direction
Example:
Projectile Motion

 The C of M of a projectile will follow a parabolic path
 The parabolic path followed is determined only as a function of
the projectile’s takeoff velocity
Maximum Height and Range
Max. vertical distance (height)
Max. horizontal distance (range)
Taking off and Landing at Different Heights
 If the human body is the projectile, a higher centre of mass can
be achieved by elongating the body at takeoff and by raising as
many body parts as possible
 The range a projectile will travel increases if the takeoff height
is greater than the landing height, and decrease if the takeoff
height is less than the landing height
Examples:
Air Resistance: force acting upon an object will change the motion
and path of object
Optimizing Range
 Increasing the takeoff height compared to the landing height
lowers the optimum takeoff angle of 45 degrees.
 Skills which take advantage of air resistance in increasing range
also have a lower optimum takeoff angle
 In most instances, increasing the magnitude of the takeoff
velocity gains the greatest increase in horizontal distance