A ping pong ball fell down into a narrow metal pipe embedded in concrete one foot deep. You have a table tennis racket (bat or paddle), a pair of shoe laces and a large unopened water bottle, which does not fit into the pipe. How can you get the ping pong ball out of the pipe undamaged?
Answer
Ping pong balls float on water. So, pour the water from the water bottle into the pipe till the ping pong ball floats to the surface.