Unit 12 Competency 2 - Examine and classify levers
Suggested Objective a: Identify first class levers and examine their uses in everyday applications
A lever is one of the simplest mechanical devices. A lever consists of a beam or stick or rod. However, a lever by itself is not effective. It must have something on which to pivot. This pivot is called a fulcrum. A lever helps to lift weights with less effort. Children on opposite ends of a seesaw lift each other's weight up and down easily. Anyone who has ever pried something loose with a crowbar or a board has used a lever.
First-class levers have the fulcrum placed between the load and the effort, as in the seesaw, crowbar, and balance scale. If the two arms of the lever are of equal length, as with the balance scale, the effort must be equal to the load. If the effort arm is longer than the load arm, as in the crowbar, the effort travels farther than the load and is less than the load.
Information and image copied from http://www.ohio.edu/people/williar4/html/haped/nasa/simpmach/lever.htm Links to an external site. on December 10, 2014
1st Class Lever.avi
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A first-class lever is a stick where the fulcrum is between the weight and the energy moving the weight (your hands, for example). Some common first-class levers are see-saws, crowbars, pliers, scissors (which use two first-class levers together), and a hammer pulling a nail.
Information and picture copied from http://scienceforkids.kidipede.com/physics/machines/lever2.htm Links to an external site. on December 10, 2014.
Suggested Objective b: Demonstrate the relation between the fulcrum, force, and load in a first class lever
Image copied from http://www.oocities.org/rjwarren_stm/College_Physics/Mechanical_Systems.html Links to an external site. on December 10, 2014.
Suggested Objective c: Construct a model of a first class lever
In the upcoming assignments, we will construct a first-class lever. Listen carefully and take good notes so you will be ready.
Suggested Objective d: Identify second class levers and examine their uses in everyday applications
Second-class levers have the load between the effort and the fulcrum. A wheelbarrow is a second-class lever. The wheel’s axle is the fulcrum, the handles take the effort, and the load is placed between them. The effort always travels a greater distance and is less than the load.
Information and image copied from http://www.ohio.edu/people/williar4/html/haped/nasa/simpmach/lever.htm Links to an external site. on December 10, 2014
A second-class lever is a stick where the fulcrum is at one end of the stick, you push on the other end, and the weight is in the middle of the stick. Some common second-class levers are doors, staplers, wheelbarrows, and can openers.
Information and picture copied from http://scienceforkids.kidipede.com/physics/machines/lever2.htm Links to an external site. on December 10, 2014.
Second Class Levers
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Suggested Objective e: Differentiate between first and second class levers by demonstrating the relationship between the fulcrum, force, and load in the second class lever
Image copied from http://www.oocities.org/rjwarren_stm/College_Physics/Mechanical_Systems.html Links to an external site. on December 10, 2014.
Suggested Objective f: Construct a model of a second class lever
In the upcoming assignments, we will construct a first-class lever. Listen carefully and take good notes so you will be ready.
Suggested Objective g: Identify third class levers and examine their uses in everyday applications
Third-class levers have the effort placed between the load and the fulcrum. The effort always travels a shorter distance and must be greater than the load. A hammer acts as a third-class lever when it is used to drive in a nail: the fulcrum is the wrist, the effort is applied through the hand, and the load is the resistance of the wood. Another example of a third-class lever is the human forearm: the fulcrum is the elbow, the effort is applied by the biceps muscle, and the load is in the hand.
Information and image copied from http://www.ohio.edu/people/williar4/html/haped/nasa/simpmach/lever.htm Links to an external site. on December 10, 2014
A third-class lever is a stick where the fulcrum is at one end of the stick, you push on the middle, and the weight is at the other end of the stick. With a third-class lever, you have to put in more energy than you would just lifting the weight, but you get the weight to move a longer distance in return. Some common examples are a broom, a hoe, a fishing rod, a baseball bat, and our own human arms.
Information and picture copied from http://scienceforkids.kidipede.com/physics/machines/lever2.htm Links to an external site. on December 10, 2014.
Physics Simple Machine Third Class Levers and Examples
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Suggested Objective h: Differentiate between first, second, and third class levers by demonstrating the relationship between the fulcrum, force, and load in the third class lever
What Is the Difference Between First, Second & Third Class Levers?
The difference between first, second and third class levers lies in the relative positioning of three items. Find out about the difference between first, second and third class levers with help from an experienced physics professional in this free video clip. Click the link
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Information copied from http://classroom.synonym.com/difference-between-first-second-third-class-levers-22834.html Links to an external site. on December 10, 2014.
The attached pdf from All Students demonstrates with pictures the difference in first, second, and third class levers. Notice the placement of the fulcrum and where force and load are as well. Take notes as needed.
Simple-Machines-Examples-with-Pictures.pdf Download Simple-Machines-Examples-with-Pictures.pdf
Information obtained from http://allstudentscanlearn.org/swhite/wp-content/uploads/2011/12/Simple-Machines-Examples-with-Pictures.pdf Links to an external site.on December 10, 2014.
Image copied from http://www.oocities.org/rjwarren_stm/College_Physics/Mechanical_Systems.html Links to an external site. on December 10, 2014.
CC7555 Simple Machines: First, Second, and Third Class Levers Mini
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Suggested Objective i: Construct a model of a third class lever
In the upcoming assignments, we will construct a first-class lever. Listen carefully and take good notes so you will be ready.