Transcript Levers

LEVERS
Week 8
What are Levers?
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A simple machine that transmits and changes
mechanical energy from one place to another
Everyday life examples:
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Pliers
Hammer
Crowbar
Wheelbarrow
In biomechanics we are interested in levers within
the human body (bones) and extended levers which
we use in sport (bats, clubs, sticks, racquets)
Examples of Levers
Sporting Levers
Function of Levers
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Increase or magnify the force applied (longer
force arm)
Generate increased speed of movement
(longer resistance arm)
Elements of Levers
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All levers consist of three parts:
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Axis (pivot point, fulcrum)
Resistance (load)
Force (effort)
The position of these parts allows us to
classify levers into:
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First class
Second class
Third class
First Class Levers
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Axis is located between the resistance and
the force
See-saw, scissors
Second Class Levers
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Axis is at the end of the lever
The resistance is between the axis and force
Wheelbarrow, bottle opener
Third Class Levers
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Axis is at the end of the lever
Force is between the axis and the resistance
The human body has third class levers
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Leg: running
Arm: bicep curl
Leg: kicking a soccer ball
The Principle of Leverage
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Velocity is greater at the end of a long lever
than at the end of a short lever
The longer the lever, the greater the velocity
at impact and the greater the momentum
developed by the object
Activities
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Cut up and paste the levers from the handout
into 1st, 2nd and 3rd lever categories
Draw and label the axis, resistance, force and
class of the following levers
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Shovel with a load of dirt on it
See-saw with 2 people on it (one light, one heavy)
A wheelbarrow full of gravel