Biomechanics 1.3a Flashcards
Newtons First Law - Inertia
-Body continues in a state of rest or velocity unless a force is acted upon it (unbalanced/external)
Newtons Second Law - Acceleration
-Bodies rate of change of momentum is proportional to the size of force applied and acts in same direction
Newtons Third Law - Reaction
-For every action there is an equal or opposite reaction
Example of First Law - Inertia
- Golf ball still unless force applied
- Or Golf ball remain constant unless force
Example of Second Law - Acceleration
-When Golf ball struck, rate of change of momentum is proportional to size of the force acted on by club
Example of Third Law - Reaction
- Tennis player hitting ball
- racquet exerts force and ball exerts an equal and opposite force on the racquet
Velocity
-Rate of change of displacement
Velocity Equation
-Velocity = Displacement/Time Taken
Momentum
-Quantity of motion possessed by a moving body
Momentum Equation
-Momentum = mass x velocity
Acceleration
-Rate of change in Velocity
Acceleration Equation
-Acceleration = (FV-IV)/Time Taken
Force
-A push or pull that alters the state of motion of a body
Force Equation
-Force = mass x acceleration
What are the types of force
- External (outside of body)
- Internal (Skeletal muscle)
What effect can force have
- Create Motion
- Accelerate a body
- Decelerate a body
- Change direction of a body
- Change shape of a body
Net Force factors
- If NF = 0
- No change in motion, forces balanced
- If NF present
- Change in motion, forces unbalanced
External Forces and what are they divided into
- Vertical forces = Weight and Reaction
- Horizontal forces = Friction and Air resistance
Weight force
- Measured in Newtion (N)
- kg x acceleration = (m/s/s)
Weight definition
-gravitational pull that earth exerts on a body
Reaction definition
-the equal and opposite force exerted by a body in response to the action force place above it
Friction definition
-the force that opposes the motion of two surfaces in contact
Net force definition
-sum off all forces acting on a body
4 Factors effecting friction
- roughness of ground surface
- roughness of contact surface
- Temperature
- Size of normal reaction
Example of roughness of ground surface (friction)
-Athletes run on rough rubber tracks
Example of roughness of contact surface (friction)
-Athletes wear spiked shoes
Example of Temperature (friction)
-Higher temperature increases friction
Example of size of normal reaction (friction)
-shot putter high mass due to N 3rd Law
Air resistance definition
-the force that opposes motion through air
4 factors affecting air resistance
- Velocity
- Shape
- Front cross-sectional area
- Smoothness of surface
Streamlining
-creation of smooth air flow around an aerodynamic shape to minimise air resistance
free body diagram
-clearly labelled sketch showing all forces acting on a body at a particular time
Centre of Mass
-the point at which an object or a body is balanced in all directions, point which weight appears to act
Stability
-ability of a body to resist motion and remain at rest, also ability to withstand a force applied and return to its original position without damage
4 Factors that effect stability
- Mass of the body
- height of COM
- size of the base of support
- Line of gravity
Mass of body effect on stability
-greater the mass, greater inertia
Height of COM effect on stability
-lower COM, greater the stability
Size of BoS effect on stability
- Greater size of BOS, greater stability
- increased by many points of contact
Line of gravity effect on stability
-More central line of gravity, greater the stability
two main functions of levers
- generate muscular effort to overcome given load
- increase the speed of a given movement
First Class lever system
- fulcrum in the middle
- E-F-L or L-F-E
Second Class lever system
- Load is in the middle
- E-L-F or F-L-E
Third Class lever system
- Effort is in the middle
- L-E-F or F-E-L
Example of first class lever system
-Extension of the neck when heading a football
Example of second class lever system
-Ball of the foot in the take-off phase of a high jump
Example of Third class lever system
-Flexion of the elbow during a biceps curl
Mechanical Advantage
- second class lever system where effort arm is greater than load arm.
- large load can be moved with a relatively small effort
Mechanical Disadvantage
- third class lever system where load arm greater then effort arm
- Large effort is required to move a small load
3 examples of technology which analyses movement
- Limb Kinematics
- Force Plates
- Wind Tunnels
Limb Kinematics
-Study of movement in relation to time and speed
Force Plates
-Ground reaction forces are measured in laboratory conditions
Wind tunnels
-steel frame buildings containing wide fans where artificial wind is produced
