THE LEVERThe Lever – a rigid bar used to gain force, gain speed or change direction.The Lever is a type of simple machine that moves about a fulcrum or pivot point, usually to help lift heavy loads much more easily (with less effort). Originally mentioned in EPISODE 1: CRUMBS, in this episode we extend our knowledge of levers. The SCIENCE CLIP shows us that the ease of lifting a heavy load is affected by where the fulcrum is. Load = the object you are liftingFulcrum = point where the lever pivotsEffort = the force needed to make the object move

EPISODE 3: CHANGING THE LIGHTBULB

LEVERS

TO TEACHERS AND PARENTSA large focus in teaching science is around encouraging both curiosity and the skills and dispositions to be able to find out or test things for yourself. This includes developing an understanding about how science itself works. The New Zealand Curriculum calls this the Nature of Science.

Tips about how to encourage these aspects are given in a

Use these to get your children talking, discussing, testing and thinking about the science involved in Jiwi’s Machines. Have fun! The science content involved in Jiwi’s Machines relates to the Physical World Achievement Aims of the New Zealand Curriculum.

INVESTIGATION: What happens to the effort needed if the fulcrum changes position when lifting a load? (This is the same thing as making the length of the lifting arm longer or shorter)

BIG SCIENCE IDEA 1: Levers can make it easier to lift a load.

BIG SCIENCE IDEA 2: The position of the fulcrum can make it easier or harder to lift a load. INDOORS OPTION: Have children use their 30cm rulers, a pencil or pen, tape, two paper cups, one larger weight and a range of objects of the same weight (eg: marbles, nuts or washers, Lego blocks, coins) to construct their own lever. The paper cups are taped or blu-tacked onto the ruler and the pen is taped to the table.

How many small marbles (or other weights) are needed in the Effort cup in order to lift two large marbles (or other weights) in the Load cup?

Establish that just as we’ve seen in Jiwi’s clips, a lever is very much like the seesaw in a playground. What happens when you are at the playground on the seesaw with an adult? Can you get them up in the air? Why not? What could you do to try to lift their heavier load?

OBSERVATIONSWhat did you observe?

Is it measurable?What might this mean?

With the 15cm mark of the ruler positioned across the fulcrum (pen), add a weight to the Load cup. Now, one at a time, count how many small marbles you need to add to lift the Load. It is unlikely to balance perfectly. You will be able to say though that it takes between x and y little marbles to lift the Load. Record this. Empty the small marbles.

Now shift the ruler so that the fulcrum is 10cm from the Effort cup. Again, how many small marbles are needed to lift the same Load? Record and empty the small marbles.Shift the ruler one last time so that the fulcrum is 10cm from the Load cup. How many small marbles are needed to lift the same Load?

RESULTS WE USED ……………. AS OUR LOAD WEIGHT WE USED ……………. AS OUR EFFORT WEIGHTS Position of fulcrum It took between _ & _ weights to lift the Load

15 cm (middle)

10 cm from Effort cup

10 cm from Load cup

OUTDOORS OPTION: The same investigation can be carried out in a BIG way outside if you have a scaffolding plank and a strong fulcrum. Big is always fun. Mind out for fingers and toes.

Make your own lever outside with the fulcrum in the middle. Put two children (Load) standing at one end. How many children (Effort) are needed to lift the Load into the air?

Now shift the fulcrum further away from the Load, approximately halfway between the middle and the Effort end. How many children are needed to lift the Load into the air? Ask the children if the same children should be used? Why?

Lastly, shift the fulcrum towards the Load, approximately half way between the middle and the Load. How many children are needed to lift the Load into the air?

Can the children relate what they have done in this investigation with what they saw in Jiwi’s LEVER CLIP? Can you now explain what happens to the effort needed if the fulcrum changes position when lifting a load?

USE EVIDENCEStudents should be encouraged to ask

and answer questions such as:

How do you know that?What makes you think so?How could you check that?

So an example of this would be...Can you think of an example

when this wouldn’t work?

JIWI WONDERS

• What other questions do you have about how levers work?

• If you had a long scaffolding or strong plank and a fulcrum, could one child lift the Principal/ Teacher / Parent off the ground? How? Try!

• Where are levers used in everyday life?

TYPES OF LEVERSDepending on the position of load, fulcrum and effort, levers can be classified into 3 types.1st Class Lever: The fulcrum is between the effort and the load eg: see–saw2nd Class Lever: The load is between the fulcrum and the effort eg: wheelbarrow3rd Class Lever: The effort is between the fulcrum and the load eg: tongs

ACTIVITY: SORT THE LEVERS!

Collect a range of different types of lever and have the children sort them into 1st, 2nd and 3rd class levers by trying them out.

The sorts of things you could collect are:1st: scissors, pliers, crowbar, hedge trimmer 2nd: nut cracker, wheel barrow, sack barrow, bottle opener 3rd: fishing rod, broom, tongs, tweezers, picture of a forearm lifting an object, stapler

EXTENSION:In EPISODE 1: TOAST BITE, the idea of Mechanical Advantage was explained. It means how much the machine multiplies the force you put into it. It is relatively easy to calculate the mechanical advantage provided by levers by using the following:MA = length from fulcrum to Effort divided by length from fulcrum to Load

Contextual Achievement Objective: PHYSICAL WORLD; Explore and investigate physical phenomena in everyday situations.

Nature of Science Achievement Objective: INVESTIGATING IN SCIENCE; Any student investigation may involve a variety of skills (pattern seeking).

Big Science Idea: Levers can make it easier to lift a weight.

The position of the fulcrum can make it easier or harder to lift a load.

Big Nature of Science Idea: Scientists look for patterns in their investigations.

Weblinks: http://scienceonline.tki.org.nz/Nature-of-science/What-is-the-Nature-of-Science/Teacher-suggestions-Investigating-in-science

http://scienceonline.tki.org.nz/Introducing-five-science-capabilities/Gather-interpret-data

http://scienceonline.tki.org.nz/Introducing-five-science-capabilities/Use-evidence

Capability focus:GATHER AND INTERPRET DATA; Are our explanations robust (based on evidence from our observations)?

USE EVIDENCE; In science, explanations need to be supported by evidence.

NZ CURRICULUM PLANNING SUMMARY

So if dE is 7cm and dL is 14 cm then MA = dE / dL = 7 / 14 = 0.5 or 1/2 - which means it is hard work to lift that load. It would be easier to lift by hand.If the fulcrum was moved to the other end however and the distances were as follows:dE is 14cm and dL is 2 cm then MA = dE / dL = 14 / 7 = 2 - which means it is twice as easy to lift that load than it would be if the fulcrum was in the middle!

Some ideas on how your body acts like a lever can be found at: http://sciencelearn.org.nz/Contexts/Sporting-Edge/Looking-closer/What-levers-does-your-body-use

Investigation – Inside optionRulersPen / PencilSellotapePaper cupsOne larger weightRange of objects of the same weight

Investigation – Outside optionScaffolding plankFulcrumVolunteers

Activity: Sort the LeversScissors, pliers, crowbar, hedge trimmer, nut cracker, wheel barrow, sack barrow, bottle opener, fishing rod, broom, tongs, tweezers, picture of a forearm lifting an object, stapler + anything else you can think of.

MATERIALS