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Foundations of Physical Science Workshop: The Lever.

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Presentation on theme: "Foundations of Physical Science Workshop: The Lever."— Presentation transcript:

1 Foundations of Physical Science Workshop: The Lever

2 The Lever CPO Science

3 Key Questions  How does a lever work?  What is the relationship between force and distance in a simple machine?  What factors balance a lever?

4 Overview  Describe how a lever works  Identify the relationship between force & distance on a lever  Apply the concept of mechanical advantage to levers

5 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

6 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

7 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?

8 A Lever in Equilibrium  Hang your weights like shown here  Does the lever balance?  What variables can be changed to balance a lever

9 Variables Involved in Levers  Amount of Input Force  Amount of Output Force  Length of Input Arm  Length of Output Arm

10 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

11 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?

12 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

13 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)

14 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


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