Pulleys

What if…

0You 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……

0PULLEY!

Pulley Exploration

0Can a pulley be used to lift a load?

0Here 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…

0Single-movable- pulley 0Can you build a pulley system that fits this description?

Advantage

0Do you remember when we used levers to reduce the effort needed to lift the load?

0 It provided us advantage.

0Did you gain any advantage by using the fixed and movable pulleys?

0How could we find out if the pulleys reduce the effort needed to lift the load?

Measure the Effort

Quick Review of the Spring Scales

0Zero the scales0Always use the scales

right side up0Add 0.5 N to scale ONLY

when pulling down

Procedure:1. Build each pulley

system (fixed and movable)

2. Measure the effort3. Record data4. Answer question 1

Pulley System Load (N) Direction of pull Scale 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?

0Pulleys can give us two kinds of advantage.

0Reduced effort is called mechanical advantage.

0Pulleys can also change the direction that the effort is applied.

0We call this directional advantage.

What kind of advantage does each pulley system provide?

Vocabulary0 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.

0Fixed Pulley: has a wheel that is attached to something above the load.

0Moveable Pulley: has a wheel that is attached to the load.

0Mechanical advantage: reduced the effort (force) needed to lift a load or over a resistance.

0Directional advantage: is a change in direction that results from passing a rope through a pulley

Content/Inquiry

0Can a pulley be used to lift a load?

0A single pulley can be set up as a fixed pulley or a movable pulley to lift a load.

0Do single-pulley systems provide advantage?

0Single fixed pulleys change the direction of effort. Single movable pulleys reduce the effort needed to lift the load.

Pulleys: Part 2

0How are fixed and movable pulleys the same?

0What 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. 0Single-Fixed 0Single-Fixed/

Single-movableSingle- Fixed/

Single Movable

Vocabulary

0Simple 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.

0What is a simple machine?Simple machines provide mechanical or other advantage.