Download First Class Lever - ms driggers

Bones as Levers
http://www.botany.uwc.ac.za/Sci_Ed/grade10/manphys/skel_mus.htm
BONES AS LEVERS!!!!
ridged pole able to rotate
A lever is a __________
or fulcrum
about a fixed point known as anaxis
___________
joint Any force
that is usually formed by a _____.
force or effort
applied to the lever is called the __________.
Simple Machines
1
3
2
4
You may not think about your _____
limbs as
being machines
_______, but they are. The action of
a muscle pulling on a bone often works like a
lever
type of ____________called
a _____.
simple machine
Most of the _____
of
the
limbs
(arms
and
bones
legs) act as levers. Bones of the body acting
advantage
mechanical ________
as levers create a __________
when it comes to ________
strength and _____.
speed
muscles
These levers are powered by _________.
5
Types of Levers in the Body
Levers are classified according to the
positions of the axis, force & resistance. There
are _____
three classes of levers. We can tell the
classes of levers apart by:
1) The axis
____________
or fulcrum that allows movement of
the action.
2) An opposing force such as a weight, which is
or load
usually called the resistance
______________.
force or effort you apply.
3) The _____________
Each of the three levers can be found in the
human body.
A force that resists the motion of the
lever, such as the downward forces exerted by
load or the
a weight on the bar, is called the _____
resistance
__________. The contraction of the
muscles is the effort
__________________and
the part of the
body that is _________
is known as the
affected
resistance or load.
In each type of lever, notice where the
fulcrum is located compared to the effort and
the load. In your body, the effort is the force
that your muscles apply to the lever. The load
is the weight that resists the pull of your
muscles.
Mechanical advantage is a measure of
how many times a simple machine multiples
______________
the effort that is applied to a load. 1st class &
2nd class levers can have a significant
________
mechanical advantage with speed and strength.
little to no advantage.
3rd class levers have _________
1
How muscles work!
The muscle exerts the ______
force for the
contracts the muscle will
lever. When it _________,
pull on the bone. This movement allows the
bones to move making them the _________.
resistance
This only can occur if the muscle is attached
to the bone with tendons
______. The place where
they attach is usually where the force is
exerted. The resistance can be increased by
adding
other objects to the bone. Movement
_______________
has to occur around a joint which is the
axis or fulcrum
_____________.
Levers in Musculoskeletal System
Lever - simple machine consisting of a
________
rigid, bar-like body that can be made to rotate
around an axis
Resistance or
load
resistance
arm
force
arm
ARF
ARF-
Axis
Resistance
Force
First Class Lever
Resistance
or load
force
arm
resistance
arm
Force or
Effort
Force or
effort
Axis or
Fulcrum
The axis is between the force and the resistance.
Axis or
Fulcrum
Examples: see-saw, scissors, crowbar
Second Class Lever
Third Class Lever
force arm
resistance
arm
Resistance
or load
force
arm
Force
or
Effort
Axis or
Fulcrum
The resistance is between the axis and the force.
Examples: wheelbarrow, wrench, nutcracker
resistance
arm
Force
or
Effort
Resistance
or load
Axis or
Fulcrum
The force is located between the
axis & the resistance.
Examples: paddling boat, digging with a shovel,
and most muscle-joint systems
2
Lever Examples
Musculoskeletal Levers –
1st Class
1st class
• Neck extension
2nd class
3rd class
Musculoskeletal Levers –
1st Class
• Gastrocnemius,
Soleus
(Pressing on the gas)
Musculoskeletal Levers –
2nd Class
R
DRA
• Gastrocnemius can
be a second class
lever when jumping
or doing toe raises.
FM
DFA
fulcrum
Musculoskeletal Levers –
2nd Class
Musculoskeletal Levers –
3rd Class
FM
• Primarily
third
class
levers
FRO
DFA
DRA
R
3
Musculoskeletal Levers –
3rd Class
Answers are to follow!!!
Since the body is made up of
mostly 3rd class levers, its
movements are adapted more
to speed than to strength.
(This is why you have to build
up your strength.)
Question Time!!!
Axis
1) A first class lever has the _________
in
the middle.
2) Give an example of a 1st class lever.
See-saw, scissors, crowbar
______________________________
3) Draw a diagram of a 1st class lever.
Resistance
Force
Axis
Question Time!!!
Question Time!!!
Resistance
_________
4) A second class lever has the
in the middle.
5) Give an example of a 2nd class lever.
Wheel barrow, wrench, nutcracker
______________________________
6) Draw a diagram of a 2nd class lever.
Resistance
Axis
Force
7) A third class lever has the _________
in
the middle.
8) Give an example of a 3rd class lever.
Paddling a boat, most muscles of the body
______________________________
9) Draw a diagram of a 3rd class lever.
Force
Force
Resistance
Axis
4
Question Time:
Examine the following diagrams.
10) Tell what is gained using levers. Explain why 3rd
class levers are not always the best to use.
Class of Lever:
2nd class lever
What is gained by using levers is a mechanical advantage.
3rd class levers have little to no mechanical advantage.
Resistance
11) Tell the type of lever we find the most in the
human body.
Axis
The class of lever we find the most in the body is the 3rd
class lever.
Reason:
R: Resistance is in
the middle
12) Explain how muscles exert force.
The muscles exert force by contracting and pulling on the
bone with the tendons. This will move the bone
(resistance) when there is a joint (axis) nearby.
Examine the following diagrams.
Examine the following diagrams.
Class of Lever:
1st class lever
Resistance
Class of Lever:
3rd class lever
Force
Force
Axis
Reason:
A: Axis is in the
middle
Force
Resistance
Axis
Reason:
F: Force is in the
middle
5