A garden hose has a flow rate of 20 litres per minute through an opening of 4 square centimetres. If a nozzle narrows the opening to 2 square centimetres, what happens to the water's exit speed?

Correct answer to question 182 (Mechanical Comprehension): it approximately doubles

Method

For a constant flow rate, speed is inversely proportional to the opening's area, so halving the area roughly doubles the exit speed.