Water flows through a circular pipe of internal diameter 3cm at a speed of 10cm/sec. If the pipe is full, how much water flows from the pipe in one minute?
If the pipe is long enough, then in 1 minute a given drop of water water will move through the pipe. Let’s pretend that instead of the water flowing out of the pipe, onto the ground or into a vat, that instead we attach another circular pipe onto the end of the the given pipe. Pretend this attached pipe is exactly 600cm long and has the same 3 cm internal diameter as the given pipe. Instead of the water flowing out of the given pipe onto the ground or into a vat, we think of the water just exactly filling this new pipe we imagine to have been placed at the end. It would then fill this new attached pipe in exactly one minute. And the amount of water in this imagined attached pipe after one minuter would be the same as the amount of water that would flow out of the pipe onto the ground or into a vat in one minute. So we need to find the volume of this imagined 600cm long pipe with 3 cm diameter. We use the formula for a cylinder: Since the diameter is 3 cm, the radius R is 1.5 cm. Since
