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Pulleys. What if… 0 You were on a construction site and needed to lift a steel girder to the fifth floor of a building, you would need the world’s biggest.

Presentation on theme: "Pulleys. What if… 0 You were on a construction site and needed to lift a steel girder to the fifth floor of a building, you would need the world’s biggest."— Presentation transcript:

Pulleys

What if… 0 You were on a construction site and needed to lift a steel girder to the fifth floor of a building, you would need the world’s biggest lever. Not very practical! Levers do provide advantage, but they aren’t appropriate for certain jobs. It would make more sense to use a…… 0 PULLEY!

Pulley Exploration 0 Can a pulley be used to lift a load? 0 Here is an example of a Single-fixed-pulley system. Single refers to one pulley wheel, and fixed means attached.

There is another type of pulley… 0 Single-movable- pulley 0 Can you build a pulley system that fits this description?

Advantage 0 Do you remember when we used levers to reduce the effort needed to lift the load? 0 It provided us advantage. 0 Did you gain any advantage by using the fixed and movable pulleys? 0 How could we find out if the pulleys reduce the effort needed to lift the load?

Measure the Effort Quick Review of the Spring Scales 0 Zero the scales 0 Always use the scales right side up 0 Add 0.5 N to scale ONLY when pulling down Procedure: 1. Build each pulley system (fixed and movable) 2. Measure the effort 3. Record data 4. Answer question 1

Pulley SystemLoad (N)Direction of pullScale Reading (N) Effort (N) Single-Fixed Single- Moveable Pull of the load Add 0.5 N if necessary Reading from the scale Draw an arrow here

Did the pulley systems provide any advantage? 0 Pulleys can give us two kinds of advantage. 0 Reduced effort is called mechanical advantage. 0 Pulleys can also change the direction that the effort is applied. 0 We call this directional advantage. What kind of advantage does each pulley system provide?

Vocabulary 0 Pulley: a wheel with a grooved rim in which a rope can run to change the direction of the pull (force) that lifts a load. 0 Fixed Pulley: has a wheel that is attached to something above the load. 0 Moveable Pulley: has a wheel that is attached to the load. 0 Mechanical advantage: reduced the effort (force) needed to lift a load or over a resistance. 0 Directional advantage: is a change in direction that results from passing a rope through a pulley

Content/Inquiry 0 Can a pulley be used to lift a load? 0 A single pulley can be set up as a fixed pulley or a movable pulley to lift a load. 0 Do single-pulley systems provide advantage? 0 Single fixed pulleys change the direction of effort. Single movable pulleys reduce the effort needed to lift the load.

Pulleys: Part 2 0 How are fixed and movable pulleys the same? 0 What kind of advantage is provided by each pulley system? A fixed pulley provides directional advantage; a movable pulley provides mechanical advantage. 0 In what way(s) are pulleys and levers the same? Lever and pulleys can provide mechanical advantage. Lever don’t move things far, but they can have tremendous mechanical advantage.

Is there any advantage to using two pulleys at the same time? E L Please diagram the single- movable- pulley system

Work with your group in PENCIL to diagram the other systems. 0 Single-Fixed 0 Single-Fixed/ Single-movable Single- Fixed/ Single Movable

Vocabulary 0 Simple Machine: is any of the six basic devices that provide mechanical or other advantage, such as pulleys and levers.

Content/ Inquiry 0 Is there any advantage to using two pulleys at the same time? Two pulleys can provide greater mechanical advantage than one when lifting loads. 0 What is a simple machine? Simple machines provide mechanical or other advantage.

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