"Let my teaching fall like rain and my words descend like dew,
like showers on new grass,
like abundant rain on tender plants."

Deuteronomy 32:2

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Tuesday, September 17

Second Grade, Science, Set Six

We are learning about and experimenting with one simple machine each week. The two books I'm using for experiments are:
  • Mighty Machines by Shar Levine and Leslie Johnstone -- experiments from this book will be denoted by (MM)
  • Simple Machines by Deborah Hodge -- experiments from this book will be denoted by (SM)

  • We started out the week by reading the book Levers by Chris Oxlade -- it teaches what a lever is, the three classes of levers, and shows many ways levers are used in everyday life. The photos in the book are large and colorful with just three or four sentences on each page.
  • (MM) page 14 -- experiments to see the three different classes of lever at work; you just need a spring scale, a rod or yard stick, a small bag of rice or pebbles, and a chair. Use the chair for your fulcrum. Use the spring scale to measure the amount of force it takes to keep the lever level when:
    • the fulcrum is in the center and the load (rocks) is at one end and the force (scale) is at the opposite end.
    • the fulcrum is at one end, the load is in the center, and the force is at the opposite end.
    • the fulcrum is at one end, the force is in the center, and the load is at the opposite end.
  • (SM) page 4 -- Table Trick -- you need a sturdy table, a chair with a strong back, a broom handle, and a volunteer or a heavy box. Have the volunteer sit or lay on the table. Put the chair with its back to the table. Use the chair back as the fulcrum and lift the table with the broom handle. You may want to have your child try to lift the table with their hands first. Have them experiment with lifting the table with different length levers. They will find that the longer the lever (on the side opposite the table) the easier it is to lift the table and volunteer.
  • (MM) page 16 -- You need four tennis balls and a bat. Go to the park (if you don't have a big back yard) and put one ball down on the ground. Put one hand close to the small end of the bat, and the other hand (second hand) as far down the bat as you can reach. Hit the ball. Get the next ball. Move your second hand up the bat a ways and hit the ball. Get the third ball. Move your second hand up the bat more and hit the ball. Repeat with the fourth ball. Which ball went the farthest? This experiment plays very well off yesterday's experiment. Also, Curious George has a good episode about leverage.
  • (SM) page 6 -- Balancing Act -- use a ruler, blocks, and a fulcrum, such as a toilet paper tube cut in half. Experiment with balancing blocks. Put some blocks far from the fulcrum and some close to the fulcrum -- Can you make it balance?
Wheels and Axles
  • We read the book Wheels by Chris Oxlade -- it tells all about wheels, axles, gears, and shows them in use
  • (MM) page 26 -- this experiment shows how adding a wheel to the axle makes turning it easier. Put two chairs back to back, about 1 foot apart. Place a broom stick across the backs of the chairs. Fasten a bucket to the broom stick with a length of string or yarn, etc. Put a small load in the bucket (we used sidewalk chalk). Turn the broom stick to raise the bucket. Then add a ruler to the end of the broomstick. (You can use tape.) Use the ruler to turn the broom stick.

  • (SM) page 10 -- Candy Collector -- Make a pinwheel with a pencil for the axle. Attach a piece of candy to a string and the other end of the pencil. The instructions have you put the pencil in two slots of a half gallon juice container, but our would not stay in place, so I made holes for the pencil and put a rubber band on one end. As the child blows the pinwheel, the string winds up and they get the candy. Just make sure the string isn't too close to the end of the pencil, or it keeps falling off. See the video below.

  • (SM) page 12 -- Bubble Race -- You will need a hand rotary eggbeater for this experiment. Half fill two bowls that are the same size. Put 1 teaspoon of dish soap in each bowl. Do not stir it. Give one person a spoon and the other the eggbeater. Let each whip up bubbles for 30 seconds. The wheels (gears) and axle of the eggbeater allow the beaters to spin fast and make more bubbles that the person with the spoon.
  • (MM) page 28 -- this experiment shows that since a screwdriver (wheel) is bigger around than a screw (axle), it doesn't take as much effort to screw the screw in. Get a piece of styrofoam and a screw. Try to screw the screw into the styrofoam with your fingers. Then try it with the screwdriver.
  • (SM) page 8 -- Whacky wheels -- make two cars by cutting a half gallon juice box in half from top to bottom. give one wheels by using colored pencils and spools. Make a ramp by placing one end of a board on a stack of books. Put both cars at the top of the ramp and let go. The car without wheels doesn't move down the ramp as well as the car with wheels because of friction. Wheels reduce the amount of friction so that the other car can zoom down the ramp.

Inclined Planes and Wedges
  • We read Ramps and Wedges by David Glover -- this book explains ramps and wedges and has lots of illustrations to show them in use.
  • (SM) page 18 -- Egg drop -- You will need two eggs, a plate, a food can, an empty aluminum foil box. Cut the top and one end from the box to make a ramp. First, place your hand on the can and drop one egg onto the plate. Next, set the top of the ramp on the can and roll the egg down the ramp. Both eggs went from the height of the can to the table, but the ramp lessened the force of the egg. The egg had to travel farther, but it had a safer landing. An inclined plane allows you to lower or lift heavy objects using less force, but you must move the object a greater distance.
  • (SM) page 26 -- Funny face -- You need a paring knife, a carrot, a soft apple (such as Golden Delicious) or a pear. Cut the carrot into 1/4" slices. Try to push a slice of carrot into the apple. Then cut a carrot slice into a point (wedge) and push the point into the apple. Which is easier?

  • (MM) page 38 -- You will need a piece of styrofoam, an unsharpened pencil, and a sharpened pencil. First, try to push the unsharpened pencil into the foam. Then try the sharpened pencil. Which is easier? The sharp end of the pencil is a wedge. The wedge changes the direction of the force: you push down, but the wedge pushes down and sideways.
  • (SM) page 20 -- Marble lift -- Make a ramp by putting one end of a board on top of a pile of books. Attach 2 yogurt cups to string or yarn. The yarn should be just a little longer than your ramp. Tie the other end of the yarn to toy trucks or cars. Put the cars at the bottom of the ramp and hang the yogurt cups over the end. start putting marbles or coins in the yogurt cups. How many does it take to pull the truck up the ramp? Change the height of the ramp. Now how many marbles does it take? The steeper the inclined plane, the more force (marbles) you must use.

  • (MM) page 32 -- Make a ramp by putting one end of a board on top of a pile of books. You will need your bag of rocks or rice (weight), a spring scale, and a toy truck. First, use the scale to pull the weight up the ramp. Check the scale to see how much effort it took. Next, place the weight at the bottom of the stack of books and use the scale to lift it to the top of the stack. Does this take more or less effort? Last, put the weight in the truck and pull the truck up the ramp with the scale. How much effort does it take? You can raise and lower the ramp to see how it changes the amount of effort if takes.
  • (MM) page 34 -- Change the length of your ramp from the above experiment (longer or shorter) and see how it effects the amount of effort.
  • The book I had requested from the library on screws had not come yet, so I read the two pages about screws in Mighty Machines.
  • (MM) page 44 -- You need an unsharpened pencil with an eraser, string (2 feet long), tack, ruler. Push the tack a little ways into the eraser. Tie one end of the string around it, then push it in all the way. Hold the pencil upright on its unsharpened end. Hold the string out so that the untied end is on the table. (The table, pencil, and string will make a triangle.) Use the ruler to measure the distance from the pencil to the end of the string. Rotate the pencil so the string winds up on it. This shows that a screw is really an inclined plane wound around a rod.
  • (SM) page 22 -- You will need a tall can (Pringles can) or a thermos, a clear plastic tube, tape, a bowl half filled with water, and food coloring. Put some drops of food coloring in the water. Tape one end of the tube to the top of your container. Hold the other end at the table top (so it makes an inclined plane). Rotate the container so the tubing winds around it in a spiral. Place one end of the container and tubing in the water. Slowly turn the can until some colored water moves into the tubing. Lift the container out of the water, tilt it slightly, and keep turning it slowly. The water will climb the tube and come out the top. If it doesn't work the first time, try holding the container at a different angle. It would be difficult to make water go up a straight tube, but the spiral makes it easier.
  • (MM) page 42 -- You need different types of screws so that you have some with ridges close together and some with ridges far apart, (we used drill bits from a set for a hand drill) styrofoam, and a screwdriver. Let your child guess if it will be easier to screw one into the styrofoam that has the ridges close or far apart. Then let them try it. The one with ridges close together should be easier. Remind them of the experiments with short and long ramps. Talk about why one screw is easier than the other.
  • (SM) page 24 -- There is a pattern in the book to make a twirling "helicopter" from paper and a paper clip. We each made one and flew them. Then I took a wadded up piece of paper and dropped both it and my helicopter from the same height. We talked about why one got to the floor faster, and likened it to the egg experiment from last week. Here is a link to the same helicopter pattern.
  • We read Pulleys by Sarah Tieck -- this book was from a different series, and I did not like it as well. It didn't give a much information as the other books.
  • (SM) page 14 -- you need a pole (broom stick will work), an empty spool, yarn or string, ribbon, plastic bucket with a handle, and the bag of pebbles that you used before. Find a place where you can set up your pole so it is supported on both ends and is level. You can use the backs of two chairs. Thread the yarn through the spool and tie it around the pole. Tie one end of the ribbon to the bucket and thread the ribbon over the spool. Put the pebbles in the bucket. Have your child lift the  bucket. Then have them pull the ribbon (using the pulley) to lift the bucket. Which is easier? A pulley changes the direction of the force.
  • (MM) page 20 -- for this experiment you need a pole at least a couple feet off the ground, two buckets with handles, a spool, a ribbon, yarn or string, and marbles or pebbles. Find a way to position the pole so it is level -- you can put each end on a chair. Put the yarn through the spool and tie it to the pole. Tie one end of the ribbon to one bucket handle. Thread the ribbon over the spool and tie the other end to the other bucket handle. One of the buckets should not be on the floor. Have your child start putting marbles in the bucket that is not resting on the floor. What happens? This shows that a single fixed pulley lets you pull in one direction and move something in the other direction. See video below, although you will have to look at it sideways!
  • (SM) page 16 -- for this experiment you need two broom sticks, a rope, and three children (so we did this at a park day). Have two children hold the sticks about one foot apart. Tie the rope to the top of one stick, then loop the rope around both sticks a few times. Have the third child hold on to the rope, when she is ready to pull, the children holding the sticks pick them up off the ground and try to pull them apart, while child #3 is pulling on the rope. Who is stronger? The child pulling the rope should be able to force the sticks together. Each time the rope is looped around a stick, it is like a pulley. Pulleys multiply the force of your muscles, giving you extra pulling power. Here is a diagram of this experiment, although they have the broom sticks horizontal instead of vertical.
  • (MM) page 22 -- set up your pole, again, tie one end of the ribbon to the pole. Tie the yarn that goes through your spool to the bucket handle. Thread the ribbon under the spool. Lift the loose end of the ribbon. This is a pulley that moves. The bucket has two supporting belts (one from pole to pulley and second from pulley to hand) this should make the bucket seem lighter. We went on from here to make a block and tackle. To do this get another spool and put yarn through the spool and tie it to the pole. The ribbon will go from the pole under the spool attached to the bucket and over the spool attached to the pole. Now you can pull down to lift the bucket, which is easier than pulling up.

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