You wake up with a gentle breeze on your face. Opening your eyes, you suddenly find that you are no longer at your home. You look around and find that you are on the roof of a very high building with no idea how you got there. You find a door, but it is locked.
You notice a paper sticking out of the bottom of the door. You open it and read-
Hey! I hope you enjoyed your morning surprise. As you might have already noticed there is only one way out of this roof and it is locked. If you want to get out you have to find out the height of the roof from the ground. Write the answer on the piece of paper and pass it under the door.
However, I'm in a good mood. So, I'll accept the answer as long as it is within 10% of the accurate height. I've also left some tools for you to use.
- Your prankster friend, Jason
Knowing that Jason only pulls the roughest tricks, you know there is no easy way out of this. You go over to the railing. You can see the ground below, but you are bad at estimating distances.
You look around and find a pendulum and a stop watch. These are what Jason left for you. There is nothing else in the roof that you can possibly use. You pick up the pendulum with your hand. It's quite heavy and has about a 20cm long string. Hum... pendulum and stopwatch, maybe I can do it, you think.
How do you find the height?
To prevent "loophole" answers the following rules hold:
- No, you don't know the height of the building.
- There is no way of communication except that piece of paper.
- The door is not breakable