Transcript
Notes: Levers
CW: Levers
H: Types of Levers
LeversApril 17, 2009
~ Archimedes
Give me a place to stand and I will move the Earth.
Objectives1. Analyze and label the parts of a lever
2. Provide examples of first, second and third class levers.
3. Calculate and determine the mechanical advantage of a lever.
Forces in Machines
A simple machine is an unpowered mechanical device, such as a lever.
A bar that is free to move about a fixed point Parts of a lever
Fulcrum – The fixed point of a lever Effort Arm – The part of the lever that the effort
force is applied to Resistance Arm – The part of the lever that applies
the resistance force
Anatomy of the lever
Input Force – Force exerted ON the lever Output Force – Force exerted BY the lever
Forces
Ideal Mechanical AdvantageWhat the mechanical advantage of a machine
would be if there were no energy lost due to friction
IMA=length of effort arm = le . length of resistance arm lr
There are 3 types of levers
1st Class Levers 2nd Class Levers 3rd Class Levers
1st Class LeverThe fulcrum is located between the Fe and the Fr. First class levers can multiply force and distance.Examples: Scissors, see-saw
2nd Class Lever
The resistance is located between the effort force and the fulcrum. These levers multiply the force but the direction stays the same.Example: Wheelbarrow
The effort force is located between the fulcrum and the resistance. The effort arm is always shorter than the resistance arm so it cannot multiply the force and the MA is always less than 1.Examples: Rake, hockey stick
3rd Class Lever