Transcript Laws and Levers - RMC Science Home

OF LAWS AND LEVERS…
LEARNING GOALS
• I will understand Newton’s three laws.
• I will understand sport and fitness examples.
• I will understand the types of levers in the human body.
WHERE TO BEGIN?
• Force – a push or a pull
• causes movement or a change in movement or direction
• vector quatities because have both a size and direction
• measured in newtons (N)
• internal and external forces
• examples?
NEWTON’S LAWS
NEWTON
• 3 laws established foundations of classical mechanics
• see Costella for a brief and likely interesting history!
1 ST LAW OF INERTIA
• “An object remains at rest or in a state of constant motion unless acted upon
by an unbalanced external force.”
• the heavier an object is, the harder it is to change it’s motion.
• this resistance to a change in motion is called inertia.
EXAMPLES
• car skidding off icy road on a curve
• gymnast maintaining a stationary pose on balance beam
• curling rock if on a frictionless surface
2 ND LAW OF ACCELERATION
• “In the presence of an unbalanced external force, an object will accelerate in
the direction of that force”.
• The heaver the body, the smaller the acceleration.
EXAMPLES
• F = ma
• as more mass is added to a blocking sled, a football lineman must generate
more force for the sled to accelerate at the same rate.
• Proper technique and strength allow professional tennis players to apply more
force when they hit the ball, causing the ball to accelerate faster.
3 RD LAW
• “Every action has an opposite and equal reaction”.
• If one object exerts a force on a second object, the second object exerts the
exact same force on the first but in the opposite direction.
EXAMPLES
• punch a wall, it punches back with the same force… you break your hand.
• kick a table, it kicks you back with the same force… you stub your toe.
• basketball or volleyball player jumping
• sprinter in starting blocks
LEVERS!
PARTS OF A LEVER
• The movement of force is the single most important concept in
understanding human movement.
Effort Arm
Effort
(force)
Load Arm
Fulcrum
(axis)
The purpose of a lever is to
gain a mechanical advantage
Load
(resistance)
ANATOMICAL LEVERS
• Levers can be found at all joints of the human body
• The force applied through muscle contraction (the pull on the movable bone
at the attachment site) is the “effort.”
• The joint where the bones come together is the axis or “fulcrum.”
• The mass to be moved by the muscle is the “load.”
3 TYPES OF LEVERS
• classification of lever based on way load, effort, and
fulcrum are positioned in relation to each other.
• result is a mechanical advantage of either increased speed
and range of motion or increased force.
1 ST CLASS
Fulcrum always positioned between load and
effort.
E
L
When fulcrum is midway between effort and load no
mechanical advantage is gained.
1 ST CLASS
When fulcrum is closer
to effort…
E
Effort must be greater than resistance of
load.
Distance the effort moves is less than
distance the load moves.
Mechanical Advantage
Increased Speed and Range of Motion
L
1 ST CLASS
When fulcrum is nearer to
load…
E
L
Effort is less than resistance.
Effort moves farther than load moves.
Lever favors force which means athlete can get more
force out than they put in.
Mechanical Advantage
Increased Force
2 ND CLASS
Load and effort are on same side of fulcrum.
E
L
Load always between fulcrum
and effort.
Effort and load move in same
direction.
2 ND CLASS
Always favor force at expense of speed or range of motion.
Effort will always increase the force applied.
Mechanical Advantage
Increased Force
3 RD CLASS
• load and effort are on same side of fulcrum.
• most common type of lever found within human body.
Effort acts between fulcrum and
load.
Effort and load pull or push in
same direction.
Movement effort results in
movement load in same direction.
E
L
3 RD CLASS
Always move load through a larger range of motion
than effort
Effort will always increase speed at which the load
moves.
Effort is always greater than load resulting in
increase in speed.
Mechanical Advantage
Increased Speed and Range of Motion
COMPLETE THE CHART
Movement
Knee Extension
Shoulder Adduction
Elbow Extension
Hip Extension
Lever Class
Effort Force
Fulcrum/Axis
Resistance
LEARNING GOALS
• I will understand Newton’s three laws.
• I will understand sport and fitness examples.
• I will understand the types of levers in the human body.