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# 17/01/2013

Mel Giedroyc listens to chapter 4 of Jacqueline Wilson's story 'Dustbin Baby,' and Dick and Dom are getting their hands dirty in How Dangerous Is Your Garden.

1 hour

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Thu 17 Jan 2013 16:00

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## Activity 1. Swing low, swing high

You might not have noticed but when you’re flying through the air on a swing, you are engaged in a battle – a battle against gravity! The force of gravity tends to pull things towards the ground, so to get up high, you need energy to overcome it.

When you start off on the swing, you use your legs to push yourself off, and this gives you energy to get the swing moving.  By pulling on the ropes and moving your legs back and forward you can increase the speed of the swing, and your motion energy, which will help you to get up higher. When the energy runs out at the top of the swing, gravity wins, and sends you back down.

Would a heavy person make the swing go faster than a lighter person? Recruit an adult and try this for yourself! You’ll find it’s possible make the swing travel faster and go higher whatever weight you are, but the size of the person on the swing doesn’t affect how long it takes to swing back and forward.

The only way you can make the swing swing more speedily, is to shorten the ropes . As Dom discovered, not only did his feet not touch the ground any more, but he swung back and forward slightly faster than before.

## Activity 2. The wheelbarrow challenge

Keen gardeners often have a wheelbarrow to move heavy items around the garden. That’s because a wheel barrow makes the job far easier. The wheelbarrow acts as a lever, which is a simple machine which allows us to lift heavy objects. The wheel is the pivot, the fixed point which the handles turn around. The longer the handles or the further from the pivot we apply a force the easier the load is to lift.

You can test this for yourself if you have two identical loads – Dick and Dom used 50kg of potatoes in bags. Try carrying the load by yourself, and notice how heavy it is. Now plonk the load in the wheelbarrow and have a quick rest! When you’re ready, try using the wheelbarrow to lift them. You should find it’s easier – in fact you may even find you can cart an adult around, if you can find one willing to volunteer!

## Activity 3. Spades and superhuman powers

Another type of lever you’ll find in the garden is a spade.

Find a piece of earth you’re allowed to dig in … Now plunge the spade into the ground, and try digging a hole with your hands held low down the shaft, not far above the metal part?

Now for comparison, move your hands to the top of the handle. You’ll find you can exert lots of pressure on the ground to dig the earth out, without much effort. That long handle is there for a reason!

A see saw is another example of a lever. If you sit close to the pivot at the centre, it’s very hard to lift your friend into the air. The further out you are, the easier it is. Even a small child could lift and adult into the air if the seesaw was long enough … As Dom said, a lever effectively gives you superhuman powers!