Lesson 13 The Lever

OBJECTIVES Balance loads on a lever. Determine the relationship between effort force and effort distance for levers. Learn how levers work. Communicate what you learn about levers to others. .

GETTING STARTED What does it mean to balance something? Draw a picture of something that is balanced How could you use a lever to lift a rock out of the ground?

Vocabulary – Lesson 13 The fixed pivot point of a lever is the (78) fulcrum. A type of simple machine that uses a small force to lift a large load is a (79) lever.

Vocabulary Load Arm The distance from the pivot point (fulcrum) to the point where the load is attached to the arm of a lever. Effort Arm Distance from pivot point (fulcrum) to the point at which the effort force is applied to an arm of a lever

Notes A lever can be a rod, board or any similar device that pivots around a fixed point called a fulcrum. The fulcrum can be anywhere along the lever’s length, but some positions are better than others for certain jobs.

Notes Levers works on the same principle as the inclined plane and pulley - - a small force acts through a large distance to do the same work as a large force that acts through a small distance.

Notes Balancing a lever works on the principle that: Two objects balance on a 1st class lever when the torques on both sides of the fulcrum are equal in magnitude and opposite in direction.

Notes Torque I the product of an applied force and the length of the lever arm. A greater torque is produce by putting the same force, farther from the fulcrum.

Types of Levers: See page 427 1st class: levers that change the direction of the input force. The fulcrum is between the input and output force. Examples: see saw, scissors, pliers, oars

Types of Levers 2nd class: levers that increase force but do not change direction of input force. The fulcrum is below the input and output force. Examples: doors, nutcrackers, bottle openers

Types of Levers 3rd class: levers that increase distance but do not change the direction of input force. Examples: fishing poles, shovels, baseball bats.

Lesson 13 QUESTION

Question – Lesson 13 How does the length of a lever affect the work done on an object? What is the relationship between effort force and effort distance from the fulcrum in a lever system?

Lesson 13 If _________________,then __________ because _________________. Hypothesis

Lesson 13 Materials 1. 2. 3. Procedure

Inquiry 13.1 Left side Right side # of washers # of holes from fulcrum

Lesson 13 Results / Data / Observations

Load force __________ x Load distance ________ = ___________ (work) The Lever Load force __________ x Load distance ________ = ___________ (work) Distance from center (# of holes) Effort Distance Effort Force Work

Lesson 13 Conclusion