In the one pulley system when you move the Mass from The 20-centimeter Mark to the 15 centimeter mark it moves to my 5cm how far did you pull the string? 5 cm
10cm
15cm
20cm

5 cm

Explanation:

Remember that in the pulley system the rope moves the same distance in both ends of the pulley, what the pulley system does is creating a mechanical advantage which basically means that it takes less effort to pull than the actual effort it would take, so for example if you have to lift a box that is 800 N, with a pulley system and the mechanical advantage you'd have to pull with less force.

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )