Category Archives: van de graaf

Levers

Archimedes (Greek mathematician, 287 to 212 B.C.) said, “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.”

Levers are the simplest of machines, simpler even than the wheel.  Unlike the wheel levers occur naturally in animal and plant life.  Lifting your arm uses several levers as does nodding your head.  The lever is simply different.

There are three types of lever.

Type 1 lever

This type of lever has a load at one end and a force at the other with a fulcrum in the middle.

Type 2 lever

This type of lever has a load in the middle and a force at the one end with a fulcrum at the other.

Type 3 lever

This type of lever has a load at one end and a force in the middle with a fulcrum at the other end.

What type of lever do these items use?  Do any of them use more than one lever to operate?

see-saw, tweezers, wheelbarrow, stapler, fishing rod, bottle opener, hammer’s claws, pliers, nut cracker, tongs, scissors, nail clippers.

Can you add anything to this list?

Now think about your own body. 

What sort of lever is required to move your head in a nodding motion?  Imagine your spine as the fulcrum, the muscles in your neck as the force and your skull as the load.

Hold your arm out in front of you and flex your bicep so that your upper arm is stationary and only your forearm moves.  What are the fulcrum, force and load and what sort of lever can you see?  Is the same sort of lever involved when you move your arm back to being straight in front of you?  Is there a different force being exerted\muscle being used?

Do all movements in the human body rely on some sort of lever or can you think of any moving parts of the body that don’t involve levers?

Activity 1

You will need:

  • An adult
  • A child
  • A brick or block of wood
  • A plank of wood 1 inch thick and at least 4 feet long

What to do:

  1. Make a lever by placing the plank over the wood block.
  2. To take advantage of the properties of the lever, make sure the fulcrum (wood block) is closer to the end of the lever on which the adult will stand.
  3. Have the adult stand on the short end and the child stand on the long end. What happens?
  4. If the child cannot lift the adult, adjust the fulcrum so that it is closer to the side on which the adult is standing.
  5. Record the weight of the adult and the child and measure the distance from the people to the fulcrum.  Can you work out the ratio for child weight and distance to adult weight and distance?

Activity 2

You will need:

  • An ruler
  • A tape measure
  • Some light food like cereal
  • A pencil
  • Some small cups

What to do:

  1. Put the ruler across the pencil.
  2. Put a piece of cereal on the end of the stick touching the table.
  3. Flip the cereal by hitting the stick end that is in the air.
  4. Mark where the pencil (fulcrum) is.
  5. Record the distance that the cereal travelled.
  6. Now place a small cup at this distance.
  7. Fire again and see if your cereal lands in the cup.
  8. Try moving the fulcrum. What happens now?
  9. Record your findings in a table.  Distance from fulcrum and distance fired.
  10. Could the other types of lever be used like this?
  11. Can you find of any inventions that operate like this?
  12. Don’t forget to tidy up your mess.

Can you think of any other experiments?

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Vortex

My lovely kids have been asking about vortexes recently.  Which way does the water spin when it goes down a plug hole? Does this change in different parts of the world?  That sort of thing.

I want to demonstrate the physics involved in an interesting way by experimentation.  Something safe and easy that the kids can do themselves that will keep their interest.  Here is what I’ve got so far from a suggestion from Prof. David Houghton that I found on t’Internet.  I would love to see some more if anyone has any suggestions.  I’d also be interested in hearing of any attempts at this experiment.

Vortex experiment

Equipment

  • Two empty clear plastic bottles.  Clean and remove all labels.
  • A rubber washer.  It should be bigger than the bottle mouth on the outside but the hole should be small.
  • Duct tape.

Method

  • Fill one bottle 2/3rds with water.
  • Place the washer on top of the bottle so the it sits over the top.
  • Put the second bottle onto the washer and tape them together firmly.  The bottles should be mouth to mouth with the washer in the middle.
  • Turn the two bottles over so the full one is on top.
  • Swirl the bottle round to start the water spinning.
  • Set the bottles down in a flat place and watch the vortex form.  One bottle should be standing upright.

Additional Notes

  • You can make the vortex more visible by colouring the water or by adding some foam beads or something that floats in the water but doesn’t block the funnel.
  • How fast can you get the water to spin?  Does this make the vortex bigger?  How do you think you could record your observations.
  • Experiment with washers of different sizes.  What happens for a wide hole or a very small one?  Record your results in a table and think of a way to present them.
  • Does the angle that the bottle is at change the vortex?  See what happens when you tilt the bottle after a vortex has formed.  Try different angles and record your results.
  • Is there any difference in the experiment if you spin it clockwise or anti-clockwise?  Record your results.

What have you observed in your experiments?  Talk about what you can see as you perform each test.  Try to predict what will happen if you change one thing (the angle of the bottles, the speed of rotation, the washer size) and then test your prediction against the evidence with a new experiment.

What does this show you about meteorology?  On a large scale what have you learnt?  If a vortex forms in a bottle of water and a vortex can form in other fluids (salt water, river water, air, cloud) where do you think you will see vortexes in the natural world?  Armed with this knowledge how could human beings use this information is something like city planning, road building or travel?

Additional Experiments

Take a large mug, a spoon and some ice. Pour some very hot water into the cup and stir it slowly in one direction so the water is rotating slowly.  You could add something to the water to see it better. 

Next place a small ice cube at the centre of the water as it rotates. With a little luck you should see the ice cube start to spin faster and faster until it is turning much faster then the water around it. 

Why do you think this is?*

The answer is below but try to work it out first and then see if you get it right.

*This occurs because the melting ice causes water to sink underneath it.   The cold water draws in some of the warm water from the top edges.  The motion of water coming in from the edges is what spins the ice cube faster.  This is the same principal which causes some tornados and whirlpools in rivers to spin up.  You may have to experiment with the position of the ice cube to make this work well. everyday items?

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Story time

I love ghost stories at Christmas.

The Winter Soltice, Alban Arthuan, or better known as Yuletime Season is a time of death and rebirth of Nature. It is said the Old Sun dies at dusk of December 21st. and when the Sun of the New Year is born at the dawn of December 22. The New Sun is thought to rejuvenate the aura of the Earth. It is like a mystical cleansing to the spirits and the souls of the dead.

A Yuletide story called the Sluagh-Sídehe of Brug na Bóinne. It translates as people of the mound or barrow where the dead have been buried.  The sídehe in the Celtic mythology and traditions are equivalent to our ghosts and goblins.  That they are the gateway for the souls and spirits of the dead and for living mortals to pass back and forth to each world.  On the other side the sídehe is the Tír na nÓg, the Land of the Youth, the Isle of the Blessed. 

Tales of ghosts, goblins and the fey folk have always interested me.  They are stories from our superstitious past where we believed that the spirits of the otherworld needed to be placated.  I love how a well made story can evoke those dark times and get the blood pumping as we imagine all sorts of unnamed things in the darkness.

I’d like to challenge my fellow bloggers to tell me a story.  A Christmas Ghost Story to frighten and entertain in the tradition of yesteryear. 

Please post your story on your own blog and comment back here so I can go and read it.  Then challenge others to do the same.  Don’t be shy, you know how talented you are.

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Third person

The beautific hoverFrog is convinced that the people of the world have today been replaced with identical copies from Tardania.  He is certain of a plot and remains on guard.

Tard (tard) – noun Slang: Disparaging

Any person who is not developmentally disabled, but rather has what is considered normal cognitive faculties but for whatever reason has opted out of using it. Whereas mental retardation is genetic in nature, this form of behavior is environmental usually resulting in too much daytime television, Brittany Spears piped in pop music, and other environmental factors.

-Urban dictionary.

Furthermore the ever honest Mr hoverFrog has been angered by the incompetence of British Telecom and of Tiscali.  He has written both companies very stern letters of complaint.  He feels certain that they will ignore the missives and continue to be incompetent.  He is trying not to let this bother him.  His letters repeated the phrase “This is no acceptable” several times.  Each time he typed this phrase he laughed out loud.

Virgin are taking over his telephone service on Friday afternoon.  He wonders if it isn’t going too far to insist that BT attempt to repair the ongoing fault tomorrow morning.  He hopes that it rains.

Finally he wonders who this third person is and may write a questioning Thursday Thirteen in a moment.

He thanks you for the time that it has taken to read this note and wishes you well.

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Another Meme

Many years ago the wonderful Sioned introduced me to this meme.  Essentially someone posts a word (in this case it would be me) and then the reader (you) rushes off to image search it.  They (you) then post an entry with the amusing picture and a new word and rush back to say that you have done so.

We all then spend oodles of time cavorting about t’Internet putting silly pictures up and much fun is had by all.

My word (as I’m starting this) is Brain and this is my silly picture.

Brain

Your word is: Ancient

I can barely contain my anticipation.  Don’t forget to leave the instructions up.

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Pirate

Tomorrow is International Talk Like a Pirate Day.  Don’t forget.

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Bog roll

Cataclismical, that paragon of virtue, has blogged about Cleanliness (which we all know is between Godliness and Good Enunciation) and I wanted to share something with you to demonstrate just how obsessive I can be.

I am the only chap in the office who changes the empty loo roll cardboardy inner thing for a new loo roll.  That isn’t the worst about me though.  If, by some chance, the loo roll has been changed by the cleaner and it is facing the wrong way, I have to turn it round.  The paper has to hang down away from the wall.

    || 
    ||        __
W ||       /      \
A  ||==|          |
L  ||       \__  / |
L  ||                |
    ||               |   <=== This side.  Very important.
    ||               |

I do this at home as well.

I don’t know what happens in the ladies though.  It is another place where I dare not tread.

Now, please pass on one of your own foibles so that I may be amused by it.  If you don’t have a foible that you wish to share I’d quite like a peccadillo instead.

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