kinematics

• what is linear motion?

  • straight or curved path, all body parts move in the same direction at the same speed (force is applied through an objects centre of gravity)
• what is distance?

  how far you go (distance travelled from start to finish)
• what is displacement?

  change in position (where you ended up relative to where you started)

  • measured in a straight line
• what is speed?

  define: distance covered for time taken

  equation: speed = distance / time
• what is velocity?


  define: change in position for time taken

  equation: velocity = displacement / time
• what is acceleration?

  define: change in velocity over a given period of time

  equation: acceleration = change in velocity / change in time (m/s^2)

  • acceleration can be positive or negative
  • positive acceleration = velocity increases
  • negative acceleration = velocity decreases
  • zero acceleration = velocity is constant
• what is angular motion?

  movement of a body or object around an axis
• what is an axis?

  a central or fixed point where the rotations occur

  • can be a body or objects centre of gravity and the body rotates around the imaginary point
  • axis can also be a real point e.g. gymnastics high bar
• what is eccentric force?


  a force applied away from an object's centre of gravity

  • when eccentric forces are applied, an object will rotate and experience angular motion
• what is torque?

  define: turning effect caused by eccentric force

  • affected by:
  • amount of eccentric force appliedhow far away from the axis the force is applied (moment arm)

  equation: torque = eccentric force x moment arm

  • greater eccentric force -> greater torque
• what is moment arm?

  arm at which a body or an object rotates around the axis (how far from centre of gravity)

  • aka lever
• what is angular distance?

  total sum of angular changes the body undergoes
• what is angular displacement?


  difference between the initial and final angular position of an object e.g. 0 degrees if returns back to original position
• what is angular speed?

  equation: angular speed = angular distance / time covered
• what is angular velocity?

  equation: angular velocity = angular displacement / time covered
• what is angular acceleration?

  equation: angular acceleration = change in angular velocity / change in time (degrees/s^2)

  • can be pos. or neg.
  • pos. acceleration - increasing angular velocity (spin faster)
  • neg. acceleration - decreasing angular velocity (slowing down)
  • zero acceleration - spin at the same rate
• what is projectile motion?

  define: movement of an object (or body) through the air

  • looks at different factors that influence the flight path of an object
  • influences:
  • gravity (works against vertical motion) - how far up or down
  • air resistance (impacts flight path) - how far left or right
  • less mass -> greater air resistance
  • more stream-lined -> less air resistance
  • greater surface area -> greater air resistance
  • more smooth -> less air resistance
• what factors effect a projectile's trajectory?

  • speed of release
  • angle of release
  • height of release
• how does the speed of release effect a projectile's trajectory?

  greater speed of release -> projectile travels further and higher
• how does the angle of release effect a projectile's trajectory?

  define: angle which objected is projected into the air from the horizontal plane

  when :

  angle = 45° (travel further on horizontal plane)

  angle > 45° (longer flight time but shorter distance - think parabola)

  angle < 45° (lshorter flight time + lower height) - more attacking
• how does the height of release affect a projectile's trajectory?

  greater height of release generally maximises the horizontal distance

  • height of release > landing height: <45°
  • height of release < landing height: >45°
• what is force?

  define: push or pull on an object

  • cause change in motion
  • measured in Newtons (N)
• what are the types of force?

  • applied force
  • frictional force
  • air/water resistance
  • gravitational force
  • drag froce
• what is applied force?

  force applied by object or body by a person or another object

  e.g. kick
• what is friction force?

  force exerted by a surface moving across another surface

  e.g. studs on a soccer pitch
• what is air/water resistance?

  drag force opposing motion of an object in air or water

  e.g. face water resistance when swimming
• what is the gravitational force?


  gravity = constant force that acts upon all objects
• what is mass?

  amount of matter object is made up of (kg)
• what is weight?

  mass x gravity (measured in newtons (N))
• what is the frictional force?

  • friction opposes motion of object
  • to cause object to move -> reduce friction
  • factors that impact friction:
  • greater mass -> greater friction
  • more rough -> greater friction
  • more surface area -> greater friction
• what is drag force?

  define: opposes motion of an object

  • influenced by body position + clothing
• what is inertia?

  define: reluctance of a body or object to change it's current state of motion

  • can be at rest or a constant velocity

  *if mass increases -> inertia increases -> force required to change object's state of motion increases
• what is momentum?


  define: a measure of the amount of motion an object has and it's resistance to changing that motion

  equation: momentum = mass x velocity

  • if an object is still it has no momentum (because velocity = 0)
• what is the conservation of momentum?

  • whenever two objects or bodies collide, the combined momentum of the two bodies is conserved
  • both objects will continue moving in the direction of the object with the greatest momentum

  e.g. ten pin bowling
• what is summation of momentum?

  define: sequential and coordinated movmenet of each segment to produce maximum force

  • to maximise momentum you can:
  • use as many body parts as possible
  • sequencing of large body parts to small
  • sequential acceleration
  • stabilisation
  • follow through
• what is impulse?


  define: equal to the change in momentum of an object

  equation: impulse = force x time

  • if impulse stays the same - to reduce force you can increase the time (e.g. giving with the ball)
  • two perspectives:
  • force reception e.g. catching a ball
  • force application e.g. throwing a ball
  • to maximise impulse you can:
  • increase the force applied to an object
  • increase time that you apply force
• what is moment of inertia?

  define: the resistance of an object to change its current state of ANGULAR MOTION (aka M.O.I)

  • dependent on: mass of object + how far the mass is distributed from the axis of rotation

  equation: M.O.I = mass x radius ^2

  • the greater the MOI, the harder it is to change its angular motion
  • can include: making an object rotate + stopping an object from its current rotation

  *kids usually use lighter + shorter equipment to reduce mass + radius -> reduces MOI
• how can the concept of moment of inertia apply to the human body?

  many athletes manipulate distribution of mass to increase/decrease MOI
• what is newton's first law of motion?

  an object will stay at rest or in constant motion unless external forces act upon it
• whawt is newton's second law of motion?

  a force applied to an object will produce a change in motion that is directly proportionaltothe size of the force and inversely proportional to the mass (f = m x a)