foundations of physical science workshop: the lever
TRANSCRIPT
Foundations of Physical Science
Workshop: The Lever
The LeverCPO Science
Key Questions How does a lever work?
What is the relationship between force and distance in a simple machine?
What factors balance a lever?
Overview Describe how a lever works
Identify the relationship between force & distance on a lever
Apply the concept of mechanical advantage to levers
Introducing… The Lever Anatomy of the lever
Fulcrum – point around which the lever rotates
Input Force – Force exerted ON the lever
Output Force – Force exerted BY the lever
Three Classes of Levers First Class - fulcrum
between Input and output
Second Class – output between fulcrum and input
Third Class – input between fulcrum and output
CPO Lever – First Class All The Way
Here we have a first class lever
The fulcrum is between the input and output
Can you get two weights to balance?
A Lever in Equilibrium
Hang your weights like shown here
Does the lever balance?
What variables can be changed to balance a lever
Variables Involved in
Levers Amount of Input Force
Amount of Output Force
Length of Input Arm
Length of Output Arm
Levers Investigation Hang weights from
the lever and get it to balance
Try 4 trials and record how many weights to hang and where you hang them
Mathematical Rule for Balancing the
Lever What mathematical relationship can you find that will balance the lever every time?
Put your rule in terms of Input and Output and forces and distances
What if there is more than one location on either side of the Lever?
What is the Relationship?
Input Force x Length of Input Arm= Output Force x Length of Output arm
Force x Distance = Force x Distance
# of Weights x Distance = # of Weights x Distance
What if there are several groups of
weights? Sum of Input = Sum of Output
(Force a x Distance a) + (Force b x Distance b) = (Force c x Distance c) + (Force d x Distance d)
Mechanical Advantage We use the same kind of relationship for all
simple machines to calculate Mechanical Advantage
Output Force/Input Force
Length Input Arm/Length Output Arm