Characteristics of Levers

Goals of the Lesson Identify class 1, 2, and 3, levers Apply mathematical formulas to find mechanical advantage and moments Design a lever to achieve balance while applying a selected force with a predetermined moment arm. Incorporate levers in a mechanical basketball player project.

Levers Babysitting 6 year old sister At playground She asks you to ride the teeter-totter. What can you do so that you can achieve a balance (neither person moving up or down)?

Levers Likely adjust position until balance is achieved Many system designs require Mathematical model solutions Testing

Mechanical Basketball Requires Basic understanding of levers Mathematical modeling tools

Parts of a Lever The Fulcrum (Pivot Point) Effort Force Load Force When Fulcrum, Load, or Effort are moved There are changes In how high the Load is lifted How much Effort is required to move the load

Classes of Levers Levers are simple machines Allows you to change Direction of motion Amount of effort needed to move a load a given distance There are 3 classes of levers

Class 1 Lever Fulcrum Teeter-Totter Located between EFFORT FORCE and LOAD FORCE Teeter-Totter

Class 2 The fulcrum is at one end, the effort is at the opposite end, and the load is between them. Moves the load same direction as the effort moves. Wheelbarrow

Class 3 Is used when desirable to have the Load move further than the Effort with the fulcrum at the opposite end. Lower arm

Mathematical Formulas We use mathematical formulas To accurately predict if a Load will move with a given Effort How much Effort will be required to move a given Load Determine the optimal points along the beam for placement of fulcrums, Loads, and Efforts

Moment Shows how the forces balance with each other Identify the effect of both force and distance Moment (also known as torque) = force x distance (distance means the distance from the fulcrum)

If we know the Effort force is 100 pounds and we are looking for the Load force (lf) that will keep the lever in equilibrium, the equation is set up as:

Mechanical Advantage Factor that the Effort force is multiplied by to create the Load force

Mechanical Advantage

Mechanical Advantage and Moment Our examples only show Class 1 Levers When evaluating Class 2 and Class 3 levers It is important to note that we still measure both of these distances or lengths from the fulcrum Even though they overlap each other for part of their lengths.

Summary How many classes of levers are there? 3 Which class has the effort placed between the fulcrum and the load? Class 3 How can we accurately evaluate the effectiveness of a lever for a given use? By experimenting with it and applying the two mathematical formulas)