The wheel and axle is one of six simple machines that provide mechanical advantage. A wheel and axle makes it easier to move or lift a load. Kids can demonstrate the concept of a wheel and axle by building a small model of a water wheel. The principle being learnt is that a wheel turned around an axle can lift a weight more easily because of mechanical advantage. Mechanical advantage means that a machine multiplies the force put into it, making the work easier for the operator.
- Skill level:
Things you need
- Plastic bottle
- Plastic straw
- Empty thread spool
- Index cards
- Paper clip
Cut the top off of a plastic bottle. The bottle's diameter must be smaller than the length of the plastic straw. Recycle the top of the bottle.
Cut two notches in the top edge of the bottle, directly opposite each other. The notches should be 1/2 inch in width and about 2 inches deep.
Cut a few holes near the bottom of the bottle so that water will be able to flow out of it when your water wheel is operating.
Cut an index card into strips width-wise. Make the strips a bit narrower than the width of your thread spool.
Fold up one of the short ends of each strip about 1/2-inch and use the folded part to tape the strips around your empty thread spool. The card strips are now sticking out at a 90-degree angle in a line around the middle of the spool. This forms the water wheel.
Insert your plastic straw through the centre of your thread spool and secure the ends with tape so that the spool cannot spin on the straw.
Rest the ends of the straw in the notches at the top edge of the plastic bottle. The straw needs to rest loosely enough that it can spin within the notches. If it is too tight to move freely, enlarge the notches.
Tape one end of a piece of string to the straw next to the spool and tape or tie a paper clip to the other end of the string. Place the end of the string with the paper clip inside the bottle.
Put the bottle in the sink and turn on a trickle of water from the tap or pour water gently over the wheel with a pitcher. As the water hits the paper blades, the wheel turns the axle, which winds up the string and lifts the paper clip.
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