Saturday, March 23, 2013

Bernoulli's principle with a Garden Hose

Learn Bernoulli's Principle while watering the backyard.   

Appropriate Age Level

Materials Needed
Garden Hose
Water Pressure
Something to Spray with Water, preferably plants, not your mom or dad. 

Science Learned
Density - mass per unit volume or the measure of how tightly passed stuff, aka mass, is. (1)

Bernoulli's Principle- states that increase in the speed of moving air or a flowing fluid is accompanied by a decrease in the air or fluid's pressure. (2)

Pressure- the measure of force applied over a unit area.(3)


1. Gather a garden hose, and hook it up to a spout.

2. Turn on the hose. Note the speed at which the water is exiting the end of the hose.

3. Now put your thumb on the end of the hose, to create only a small slit for the water to exit. The water should now exit the hose at a faster speed.  This is demonstrating Bernoulli's Principle. (4)

4. While watering plants, explain: You have to press your thumb hard against the end of the hose because the water in the hose is under greater pressure in the hose than outside of it.  The pressure in the hose is definitely greater than that of the atmosphere outside the hose.

5. You can make the hole on the end of the hose increase or decrease in size and as the hole decreases in size the speed of the water will increase because there is a larger pressure differentiation and the water wants to get to the lower pressure state as quickly as it can.

6. Enjoy your nicely watered garden all thanks to Bernoulli's Principle!

Time Allotted

5-10 minutes

4. Serway and Beichner Physics for Scientists and Engineers 5th Edition. 2000. p. 471.