LeversInvestigation 1

Part 1: Introduction to Levers

0Lever: are tools that people use to make work easier. Levers give us an advantage by making work easier.

Lever Arm: a stick or beam, free to pivot at a point

Fulcrum: is the point around which the lever arm pivots.

More vocabulary:0The mass lifted by the

lever is the Load.

0Effort: is the force (push or pull) needed to lift or move the load

The challenge…

0Set up a lever system with the load hanging at 15 cm.

0Can you lift the load with one finger?

0Does it always take the same amount of force to lift the load?

0Where should you press to lift the load with the least force?

Advantage

0What advantage can be gained by using a lever to lift a load?

The advantage provided by the lever by a lever is that it is easy to lift the load if you apply the effort FAR from the fulcrum.

0How can you measure the advantage provided by the lever?

Spring scales can be used to measure how much effort is needed to lift loads. Effort is a force, and force is measured in newtons.

Spring Scales

Demonstration Lever and Spring Scale

Rules for Using Scales0 Always zero the scaled before

starting0 Always use the scale right side

up, never upside down.0 Pull until the lever arm is level,

then read the effort. This works best if one student pulls the scale while another reads the effort.

0 STOP before the scale goes past the 10-N limit.

Measure Force

Distance from Fulcrum

Force Needed to Lift Load

5

10

15

20

0What is the relationship between the load and effort that gives a lever user the greatest advantage, that is, makes it easiest to lift the load?

When the effort is applied at a great distance from the fulcrum, the load is easier to lift.

Vocabulary:

0A LEVER is a simple machine that people use to gain mechanical advantage, such as making work easier.

0A LEVER ARM is a stick or beam free to pivot at a point0The FULCRUM is the point where the lever arm pivots.0The mass lifted or the resistance overcome by a lever is

the LOAD.0Effort is the force needed to move a load or overcome a

resistance.0Effort is measure in newtons.

Content/Inquiry

0 What are the four parts of a lever?

Lever arm, fulcrum, load, and effort

0 In what way can a lever provide an advantage?

It can make a load easier to life, it can move loads, and it reduces effort.

0What is the relationship between the load and effort that gives a lever user the greatest advantage?

In a lever system the farther from the fulcrum the effort is applied, the greater the advantage to the lever user.

Investiagtion1: Part 2

0How much force (effort) is needed to lift the load?

A scale is a useful tool for measuring the amount of force needed to lift a load. Force is measured in newtons.

0Load Stays at 10 cm0Effort is applied at various distances from

the fulcrumPosition of Effort

(cm from fulcrum)Effort

(Scale + 0.5 N)

2.5 cm 9.4 N

5.0 cm 4.5 N

10.0 cm

15.0cm

20.0 cm

25.0cm

DemonstrationLoad 5 cm from the fulcrum

Scale 25 cm from fulcrum on other side

0The load is 5 cm from the fulcrum. How much pull is being applied to lift the load?

0.0NThe load is being lifted

with no effort. How is that possible?

0 If the weight of the scale is lifting the load, how can we find out how many newtons that is?

Calculate Total Force

If the scale itself pulls with a force of 0.5 N, what is the total pull applied to the lever system in each measurement in experiment A?

The scale reading does not include the 0.5 N pull of the scale itself. The total effort is the sum of the reading on the scale PLUS the 0.5 N pull of the scale.

Position of Effort(cm from fulcrum)

Effort(Scale + .05 N)

2.5cm 9.4N

5.0 cm 4.5 N

10.0 cm

15.0 cm

20.0 cm

25.0 cm

Begin Experiment…

Remember to keep load at 10 cm

RECORD each time you move your effort.

Any benefit you can get from using a lever is called an advantage.

0Did the lever give you any advantage?

0Did the amount of force needed to lift the load change when you moved the position of the effort?

0What is he relationship between the position of the effort and the amount of effort needed to lift the load?

The farther the effort is from the fulcrum, the easier the load is to lift (force advantage); the closer the effort is to the fulcrum, the harder it is to lift the load.

TWO-COORDINATE GRAPH

0A two-coordinate graph is helpful for understanding relationships and making predictions. The x-axis on the bottom describes what you changed during the experiment. In this case, you changed the location of the effort.

0Y-axis always shows what you find out, in this case how much effort it takes to move the load.

Describe Relationships

0What general statement can you make about your graphs?

0What is the relationship between the load and the effort in a lever system?

The load is easier to lift as the effort is applied farther from the fulcrum.

Make Predictions

0How much effort would it take to lift a load at 10 cm if the effort were at 22 cm? At 13 cm? At 30 cm?

0 If 4.0 N of effort was required to lift the load at 10cm, where was the effort applied?

Vocabulary

0Two-coordinate graphs show relationship between two variables.

0Advantage is a benefit obtained by using a lever (or other simple machine)

Content/Inquiry Entries

0When the load is at a constant position on the lever arm, how can you make it easier to lift the load?

The farther the effort is from the fulcrum, the easier it is to lift the load.

0What is the difference between the weight of the load and the amount of effort needed to lift it?

The weight of the load remains constant; the effort needed to lift the load varies depending on where the effort is applied on the lever arm.

Investigation 1: PART 3

0What is the relationship between effort and load, and how the relationship can be used to their advantage when lifting a load?

What do you think would happen to the effort needed to lift the load if…

0 the scale stayed at one location on the lever and…

0 the load moved farther and farther from the fulcrum?

Would the result be the same as moving the location of the effort?

Experiment B

0Predictions: 0Begin Experiment!

Graph Results on Two-Coordinate Graph

0X-axis is reserved for the independent variable- what they changed during the experiment

0Y-axis is reserved for the dependent variable- what they found out.

Discuss Results

0How does your graph of Experiment A compare to your graph of experiment B?

The graph of experiment B starts at (0,0) and is a straight line.

0What is the relationship between the location of the load on the lever system and the effort it takes to move it?

The effort needed to lift the load decreases as the load gets closer to the fulcrum.

Predictions

0How much effort would it take to lift a load at 10 cm if the effort were applied at 22 cm? At 13 cm? At 30 cm?

0 If a 4.0 N effort were required to lift the load at 10 cm, where was the effort applied?