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 examples? 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!

1st 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

2nd 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.

3rd 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 Load Effort Arm Load Arm Effort The movement of force is the single most important concept in understanding human movement. Effort Arm Load Arm Fulcrum (axis) Effort (force) Load (resistance) The purpose of a lever is to gain a mechanical advantage

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.

1st class Fulcrum always positioned between load and effort. When fulcrum is midway between effort and load no mechanical advantage is gained.

1st class When fulcrum is closer to effort… Mechanical Advantage Effort must be greater than resistance of load. Distance the effort moves is less than distance the load moves. Increased Speed and Range of Motion Mechanical Advantage

1st class When fulcrum is nearer to load… E L Mechanical Advantage 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

2nd class Load and effort are on same side of fulcrum. Load always between fulcrum and effort. Effort and load move in same direction.

2nd class Mechanical Advantage Increased Force Always favor force at expense of speed or range of motion. Effort will always increase the force applied. Mechanical Advantage Increased Force

3rd class Effort acts between fulcrum and load. load and effort are on same side of fulcrum. most common type of lever found within human body. E L Effort acts between fulcrum and load. Effort and load pull or push in same direction. Movement effort results in movement load in same direction.

Increased Speed and Range of Motion 3rd 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 Lever Class Effort Force Fulcrum/Axis Resistance Knee Extension Shoulder Adduction Elbow Extension Hip Extension

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.