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8th Science & Health
8th Science & Health
Pages and Files
Human Body Systems
POPS questions & answers
Properties of Matter
Forces, Energy, & Motion!
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Lesson 6 Inclined Planes
Lesson 7 Pulley Systems
Lesson 8: Levers
1) Think about how to balance something
2) Describe ways to use levers to move something
3) Study characteristics of lever to describe how they work
4) Balance loads on a lever
5) Determine the relationship between effort force and effort distance for levers
1) A lever has 2 arms
2) A lever has a fulcrum about which the 2 arms rotate
3) On a lever, torque is the product on an applied force and the length of its lever arm
4) A lever is balanced when the magnitude of torque on the left lever arm equals the magnitude of torque on the right lever arm
5) A lever is a simple machine
6) Machines reduce effort force and increase effort distance when doing work
7) A 1st-class lever has the fulcrum between the load and the applied force
8) A 2nd-class lever has the load between the fulcrum and the applied force
9) A 3rd-class lever has the applied force between the fulcrum and the load
Students discuss the meaning of balancing an object. Students describe how to use a lever and identify the parts of a lever. Students balance washers on a lever and develop a rule to balance different numbers of washers on a lever. Students use a lever to lift the K'NEX sled 0.10 meter. Students investigate how the effort force is related to position on the lever arm where the force is applied to lift the sled.
balance, fulcrum lever, lever arm, effort distance, effort force, load distance, load force, work, 1st-class lever, 2nd-class lever, and 3rd-class lever
In this lesson, students continue to study simple machines. Students investigate the properties of a lever by exploring how levers balance objects and reduce the effort force needed to lift a load. Students clarify their understanding of the lever and recognize the role of the fulcrum. To identify factors that determine whether the lever will balance, they put 4 washers at a fixed location on the lever's left arm and balance them with different combinations of washers placed in the appropriate position of the right arm. Then, students investigate effort force and effort distance relationships for machines as they did in Lessons 6 & 7. Students then use their data to compute work done to lift the K'NEX sled to a height of 0.10 m. On the basis of these exercises, students refine their definition of a machine and see that the lever is a simple machine.
Levers can use a small force to lift a large load. A lever lets a person or another machine use less force to raise and object vertically or move it horizontally. A lever can be a rod board, or any similar device that pivots around a a fixed point, called a fulcrum. The fulcrum can occur anywhere along the lever's length, but some positions are better than others for certain jobs. THere are 3 kinds of levers- 1st-class, 2nd-class,, and 3rd-class levers. The difference between these classes is based on the position of the fulcrum and where the effort force is applied.
In this lesson student use only a 1st-class lever. Many people are familiar with these levers: seesaws, oars, and pliers are examples. On the 1st-class lever, the fulcrum is between the load force and the effort force. This type of lever works on the same principle as the inclined plane and the pulley- a small force acts through a large distance to do the same work as a large force that acts through a small distance.
1st, 2nd, & 3rd-class levers!
Levers in the Human Body!
Identify Levers Page
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