Transcript LEVERS - Western Springs College .::. Welcome

LEVERS
A lever is basically a rigid structure, rotating around a
fixed point.
A lever consists of three parts :
 1. Load (resistance)
 2. Effort (force)
 3. Pivot (fulcrum)
List the two main functions of a lever :
◦ To move greater loads with a set amount of force e.g
levering a heavy box with a crowbar
◦ To help move loads at greater speed eg golf club or a
badminton racquet.
Levers
• External levers allow force and speed to be applied from
outside the body
• the oars of a boat
• the pole used in pole vaulting
• Internal levers are inside the body and are the most important
levers for human movement
• Joint = fulcrum
• Bones = lever arms
• Muscles = effort
Internal and External Levers
levers
There are 3 types of levers, fill in the grid below
Class
Illustration
Definition
Examples
First
The pivot lies
between the effort
and the load
See saw, crowbar
Oar in a boat
Second
The load lies
between the pivot
and the point of
effort
Wheel barrow,
Opening a door by
the handle, diving
board, press ups
Third
The effort lies
Biceps curl, softball
between the load and bat, badminton
the pivot
racket
•
•
•
•
Are the most common lever type in the human body
They allow for more speed to be produced
Shorter lever for strength e.g. gymnastics rings
Longer lever for speed e.g. straight leg when kicking ball
THIRD CLASS LEVERS
• A force arm (FA) is defined as
• The distance from where effort is applied to the pivot (e.g.
muscle attachment to the joint)
• A resistance arm (RA) is defined as
• The distance from the load to the pivot
LEVER ARMS (bones)
• What is the advantage of using a racket in badminton?
• Lengthens the lever therefore longer RA
• Longer RA = higher velocity or speed can be attained when
hitting the shuttle
• Speed is transferred into the shuttle!
THIRD CLASS LEVERS
Same for both.
3rd Class lever
Pivot = shoulder
joint
Effort = deltoids
Load = racket head
THIRD CLASS LEVERS
• How does altering the RA (bending and then
straightening joints) make badminton shots more
effective?
• Bending arm reduces lever length allowing lever to generate
more force and to be rotated with more speed
• When straightened, speed at end of lever is maximised
allowing racket head to travel at full speed.
• Used to strike the shuttle faster and propel it forward at high
speed!
THIRD CLASS LEVERS