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Can you explain this?
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Can you explain this?
 
Here are a few tests to try at home. If you can explain how they work, please email us. A selection of the best ones will be posted here . Here's a clue to get you started: Sir Isaac Newton and his three laws of motion have something to do with them.

Coins on your elbow
 Card and coin
 In a spin
 Tablecloth yank
 Gyroscopes

Coins on your elbow
Can you really catch coins that have been balanced on your elbow? Yes you can, with a little bit of practice and some help from Newton.

You will need:

5 coins of the same size - the heavier the coins the better
1 elbow - your own will do

  1. Hold your elbow up in the air like in the picture. Make sure your forearm is parallel to the ground and your hand is near to your shoulder.
  2. Balance one of the coins on your elbow.
  3. Quickly move your elbow downwards and sweep your hand forwards trying to catch the coin. Catch the coin with the hand of the arm on which the coin was balanced.
  4. Once you can do the trick with one coin, try it with several coins stacked up on your elbow.

Coins on your elbow picture

Once you've mastered this trick tell us how it works by sending us your answer. A selection of the best explanations will be posted here.

Card and coin
Here's one trick that is easy to carry round with you.

You will need:

1 coin, the heavier the better
1 playing card, or business card
  1. Turn one of your hands so it is palm up. Form a fist but extend your forefinger.
  2. Balance the playing card on the tip of your finger. Place the coin in the centre of the card so the card and coin balance.
  3. Flick the card using your other hand. You should see the card go flying off while the coin stays carefully balanced on the tip of your finger. It can take a bit of practice to get this right. Make sure your flick is level with the card and is not flicking it up or down.
  4. Try using different materials such as sandpaper or thin plastic, try polishing the card - when is it harder or easier to flick the card without disturbing the coin?

Card and coin picture

Once you've mastered this trick tell us how it works by sending us your answer. A selection of the best explanations will be posted here.

In a spin
 How can you tell the difference between a cooked egg and a hard-boiled egg without breaking their shells? It's all down to Newton's laws of motion.

You will need:

A hard boiled egg (boil for about 10 minutes - ask an adult to help with this)
A raw egg (take care not to break it)

  1. Put both eggs on the middle of a table.
  2. Spin both eggs at the same time.
  3. Gently touch both eggs with your forefingers, take your fingers away straight away.
  4. The cooked egg stops spinning. But why does the raw egg start to spin again?

In a spin picture

Once you've mastered this trick tell us how it works by sending us your answer. A selection of the best explanations will be posted here.

Tablecloth yank

Can you pull away the tablecloth from a table and leave the settings undisturbed? There is no trickery involved - it is all down to Newton's laws of forces and motion! We suggest you try this easier version before you start on a fully laid table.

You will need

1 Empty plastic fizzy drink or water bottle (with lid)
1 Piece of cloth without hems or seams (approximately 20cm x 60cm)

  1. Fill the bottle up with water and put the lid on. Make sure the outside of the bottle is dry and there are no leaks.
  2. Place the cloth on a table or other flat surface. Put the full bottle on the cloth.
  3. The moment of truth! Grasp the end of the cloth tightly with both hands. Quickly pull out the cloth from beneath the bottle with an action as quick as you can muster. Try to keep your arms at the same level as the table-top.
  4. Stand back and accept the rapturous applause from your amazed family and friends! The bottle should still be in the same place on the table while the cloth is in your hands.
  5. Now repeat the experiment but put less water in the bottle. Is it easier to do when the bottle is full or empty? Why?

Tablecloth yank picture

Once you've mastered this trick tell us how it works, including why having the bottle filled with different amounts of water makes a difference, by sending us your answer. A selection of the best explanations will be posted here.

Gyroscopes
 Gyroscopes seem to defy gravity once they are spinning. Can you explain how they do this?

You will need:

1 gyroscope with string

  1. Wind the string tightly around the spindle of the gyroscope.
  2. Hold the gyroscope firmly by the ends and pull the string all the way out as quickly as you can.
  3. The gyroscope should be spinning freely. Put it onto the stand and see it remain upright.
  4. Repeat steps 1 and 2, but this time balance the gyroscope on the end of your finger so the spindle is parallel to the floor. You should see the gyroscope stay balanced parallel to the floor.
  5. Repeat steps 1 and 2, once the gyroscope is spinning move it around and feel the forces acting against your hands.

Now that you have seen some of the effects of the gyroscope tell us how it works by sending us your answer. A selection of the best explanations will be posted here.