 Are your marks? Get set? Go! Hello and welcome to Do Try This at Home, brought to you by the Institutes of Physics. We're making these films for parents and carers across the UK and Ireland so that you can explore science together at home with your kids. My name's Melissa. Welcome back to my living room and today I have a gravity-defying challenge for you and your family that I call Ping Pong Pickup. Each competitor is going to need an empty bottle, I'm using a 2 litre Fizzy Pop bottle, some cellotape, a marker pen, some ping pong balls, a pair of scissors, a bowl and something circular to draw around that's wider than a ping pong ball but not as wide as your bottle. To make your picker upper, use your marker to draw a line around the curved part of the bottle. Now we're going to have to make a hole in the bottle. I'm going to use a pair of scissors to pierce it and adults should definitely do this part. Then carefully cut around the bottle and add little bits of sticky tape to cover any jagged edges to make it extra safe for little hands. Take your bottle and place it over your ball and then start to spin your bottle in fast circular motions like this. And once you've got your ball spinning lift your bottle up and then take your bottle over to your ball and drop it in. My top tips are, spin the bottle quickly and lift the bottle vertically. The challenge here is to get the ball as quickly as possible from table to ball. Then challenge your friends and family to a game of Ping Pong Pickup. I'm going to call my friend James now. Hi James! Ready? I was born ready. On your marks, get set, go! I'll keep up with the practice James. What's going on here and how can you explain it to your family? The curved lip of our picker upper is the key. You can prove it by using a container with straight sides like this. There's no pickup. When we spin a ball inside a container it wants to fly out. It pushes up against the wall of the container and the wall pushes back. It's this push that makes the ball go round in a circle. The faster we make it go, the bigger the force. But to lift it up we need to overcome gravity. So we need an upward push. That's why our curved surface works. It pushes in this direction along the diagonal which is equivalent to a force this big sideways and this big upwards. And if we spin the ball quickly enough the upward part becomes big enough to balance gravity. And that works with any round object inside the container that has a mouth narrower than its body. Don't worry if you're not totally sure about the science. As always have fun challenging your friends and family and then head over to our website for more information. Well that's it for this time so it's goodbye from me and it's goodbye from James.