Transcript Biomechanics - Principles of Levers

Biomechanics
Principles of Levers
Principles of Levers
Aim:
To understand how the three types of
levers work and appreciate the
advantages/disadvantages of each
one.
Principles of Levers
Expected Knowledge
• Force
• Velocity
Principles of Levers
Key Vocabulary
• Lever
• Fulcrum
• Resistance
• Effort
Levers are…
• Simple machines that help us apply
force.
• Rigid structures, hinged at some part with
forces applied at two other points.
We have levers within our body, and also
use them externally for many different
reasons.
All levers have three parts:
• Fulcrum
• Resistance
• Effort
Fulcrum
The pivot point.
Resistance (or load)
The weight that needs to be moved.
Effort
The force that is applied to move the
resistance (or load).
Functions of a Lever
Levers perform two main functions:
To increase the resistance
(or force) that can be moved with
a given effort e.g. a crowbar.
To increase the velocity at
which an object will move with a
given force. E.g. A golf club.
Classes of Levers
There are 3 classes of levers.
Each is structured in a different manner
and has different advantages.
First Class Levers
The fulcrum lies between the effort and the
resistance.
First Class Levers
Using a crowbar to move a rock.
First Class Levers
Using a hammer to pull out a nail.
First Class Levers
A see-saw.
First Class Levers
Up and down movement of the
head about the atlas joint.
First Class Levers
Pulling an oar in a row boat.
Second Class Levers
The resistance lies between the fulcrum and
the point of effort.
Second Class Levers
The movement of the foot when walking.
(the calf muscle provides the effort and the ball of the foot is the pivot)
Second Class Levers
Opening a door by
the handle.
Second Class Levers
Opening a bottle with a bottle opener.
Second Class Levers
Pushing a wheel barrow.
Third Class Levers
The effort lies between the resistance and
the fulcrum.
Third Class Levers
Biceps curl.
Third Class Levers
Fishing with a rod.
Third Class Levers
Swinging a bat to hit a ball.
Application
Long levers
provide amplified power at the
expense of speed of movement of the object
being moved.
Examples:
– Using a jack to lift a crashed car.
– Using a knife to get the lid off a tin.
Application
Short levers
provide speed
at the expense of power
Example:
Levers designed to accelerate objects include:
- Most body limbs used for throwing or kicking
because the muscle inserts near the pivot
point.
Application
• Can you think of sporting examples where
there are longer and shorter levers?
• What happens to the effectiveness of a
lever if the fulcrum is moved closer or
further away from the load?
Revision
Question One: Fill in the blanks
Levers are simple machines which helps us apply
____(a)____ . They have ___(b)___ parts. The ___(c)___
is the pivot point. The ___(d)___ (or load) is the weight that
needs to be moved. The ___(e)___ is the force that is
applied to move the resistance.
Revision
Question Two: Label the diagram
Revision
Question Three: First, Second or Third Class?
(a)
The effort lies between the resistance and
the fulcrum.
(b)
The fulcrum lies between the effort and
the resistance.
(c)
The resistance lies between the fulcrum
and the point of effort.
Revision
Question Three: First, Second or Third Class?
(d)
(f)
(e)
Revision
Question Three: First, Second or Third Class?
(g)
(h)
(i)
(j)
Revision
Question Three: First, Second or Third Class?
(k)
(l)
(m)
(n)
Application
• How would you change your grip on a softball
bat if you wanted to hit the ball with more force?
Experiment with this with a partner.
• With a partner find another physical activity
example that will be able to demonstrate
application of the principles of levers, showing
what happens when you change the length of
your lever.