### Shot Under Pressure

SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-on Activity Training
TeachEngineering Hands-on
Activity:
*A Shot Under Pressure
http://www.crt.state.la.us/parks/ibyusegne.aspx
TeachEngineering Digital
Library:
teachengineering.org
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
TeachEngineering Digital Library
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• The TeachEngineering digital library provides free,
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• Engineering lessons connect real-world experiences
with curricular content already taught in K-12
classrooms.
• Mapped to educational content standards,
TeachEngineering's comprehensive curricula are
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daily lives.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
• Be prepared! Do each activity beforehand
• Make sure all materials are available
• Be flexible
• Have Fun!!
http://commons.wikimedia.org/wiki/File:Watergun.jpg
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Full Activity on TeachEngineering
• Fluid Dynamics, Bernoulli’s Equation
• Engineering focus:
o Engineering Research/Analysis
• Students use their understanding of projectile physics and fluid dynamics
to find the water pressure in water guns.
• By measuring the range of the water jets, they are able to calculate the
theoretical pressure.
• Students create graphs to analyze how the predicted pressure relates to
the number of times they pump the water gun before shooting.
• Learning objectives:
o Use projectile motion physics to determine the initial velocity of a projectile
launched horizontally.
o Use Bernoulli's equation to find the pressure of a fluid.
o Collect, record and analyze data to determine relationships among
variable.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
•
Suggested time: 120 minutes (can be modified for 60
•
•
Suggested group size: 3 students/group
Materials
minutes)
o
o
Each group needs:
• water gun with a pumping mechanism (for example, Super
Soaker Water Blasters; available at stores such as Target, Kmart,
WalMart or online; ~\$10 each); ask students to bring in their own,
if possible
• moveable desk or table, on which to mount the water gun
• duct tape
• tape measure, long enough to measure 35+ feet (11+ meters)
• (optional) chalk or tape, to mark off every 10 meters of the
shooting range
• pen or pencil
• Take Your Best Shot Worksheet, one per student
• (optional) Evaluation & Enhancement Worksheet, one per
student
• (optional) computer with Microsoft Excel
For the instructor:
• Evaluation & Enhancement Worksheet Answers
http://www.teachengineering.org/view_activity.php?url=col
lection/cub_/activities/cub_bernoulli/cub_bernoulli_lesson01
_activity1.xml
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Engineering Connection (Real World Application):
• Biomedical/Civil Engineering
• When engineers design water amusement park rides, water
fountains, or anything that involves shooting water, they use
a similar modeling process to determine where water jets will
land; this ensures the safety and best experience for its users.
• More generally, Bernoulli's equation is used by any engineer
working with fluids.
• For example:
o Biomedical engineers use this principle to model the flow
and pressure of bodily fluids
o Civil engineers use it to determine the size of pipes
needed to get water to people's homes and workplaces,
or run industrial processes.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Vocabulary Terms
Definitions/Equations
incompressible
A fluid that does not compress, or in other words it has a constant
density.
inviscid
Effects from the viscosity of a fluid are ignored.
range
Horizontal distance traveled by a projectile.
streamline
A line tangent to the direction of flow in a fluid that illustrates how
fluid flows around an obstacle.
viscosity
The internal friction in a fluid. Fluids with high viscosity are thick and
slow (such as molasses), while those with low viscosity (such as alcohol)
are thin and fast.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Activity Background:
Bernoulli’s Equation
o An important expression that relates pressure, height and velocity of a fluid
at one point along its flow.
o A fluid's pressure decreases as its velocity increases; The Bernoulli equation
puts this relationship into mathematical terms and includes a term for fluid
height.
o Example: Think of water moving down a water slide. At the top (where you
load), the water is slow moving, pushed only by the water behind it. When
the slide drops, the water rushes down quickly, increasing speed as it falls.
Thus, the velocity is also affected by gravity through height.

o Bernoulli’s equation:  +  +  = , where ν = velocity,  =

fluid density,  = relative height, and  = pressure
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Activity Background:
Finding the Pressure in a Water Gun
o
Bernoulli's equation can determine the pressure inside the water gun, but first you
have to know how fast the water coming out of it is moving - velocity.
o
Water leaves the water gun in the horizontal direction, so its total velocity can be
reduced to horizontal velocity ( ). A simple relationship relates the horizontal velocity
( ) to the distance () it travels in a certain amount of time ():
Equation 1
=  ∗
o
The distance can be measured, but we need to calculate time using another
equation that relates time to the initial and final vertical positions of the water (0 and
), the initial vertical velocity (0 ), and the vertical acceleration,  :
= 0 ∗ 0  +
o

2
2
Equation 2
In this problem, Equation 2 simplifies to:
ℎ=
o
1
1
2
2
Equation 3
Once time () is solved for, it can be plugged into Equation 1 to solve for velocity ( =
)
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Activity Background:
Finding the Pressure in a Water Gun (cont.)
o
Once velocity is found, we can solve for pressure using Bernoulli's equation. We can
set the Bernoulli equation at two points equal to each other as shown in the equation
below:
1
1
1 2 + ℎ1 + 1 = 2 2 + ℎ2 + 2
2
o
2
For this particular problem, two useful points to choose are the inside of the gun
(position #1) and the outside of the gun at the nozzle (position #2). These points are
chosen because we know that the velocity of the water inside the gun (1 ) is initially
zero, and that the pressure outside the gun (2 ) is the atmospheric pressure (~101,000
Pa). The density () is the density of water, and the relative heights (ℎ1 and ℎ2 ) are
equal if the gun is level. Using algebra, the pressure inside the water gun is easily
solvable!
http://www.teachengineering.org/view_activity.php?url=collection/cub_/activities
/cub_bernoulli/cub_bernoulli_lesson01_activity1.xml
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Before the Activity:
o
Gather materials. If possible, ask students to bring
their own super soaker water guns from home.
o
Make copies of the Take Your Best Shot Worksheet
and (optional) the Evaluation & Enhancement
Worksheet.
o
Find an appropriate location to shoot the squirt
guns. It is best to secure a relatively open space
(to better see where water lands).
o
Set up a table or desk so it is level, and mark off with
chalk or tape the distance from the table every
meter for ~10 meters.
http://commons.wikimedia.org/wiki/File:Super_Soaker_CPS4100.jpg
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
With the Students:
1. Class Discussion:
Most popular water guns today use a hand pump to build up air pressure and shoot water out of
a tube, often in order to soak your friends and family while looking totally awesome. How much
pressure do you think it takes to have this fun? How would one even go about calculating that?
The following activity answers those questions, but first, what do you think?
2. Hands-On Experimentation - Prep! Have students do the following:
a. Fill your water gun with water. Pump it a couple of times and shoot it, then top it off. So the
water gun works properly, leave a small amount of air in the tank.
b. Mount your water gun on a sturdy surface approximately a meter above the ground. The
gun should be mounted on its side and secured with duct tape. Once secured, make sure
you can still squeeze the trigger and move the pump.
c. Measure the height of the nozzle above the ground.
d. Designate one group member to be responsible for marking where the water lands.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
With the Students:
3. Hands-On Experimentation - Testing! Have students do the following:
a. Pump the water gun the number of times you have decided for your first trial (see data table
below), and shoot the water. Hold the trigger until the water has stopped coming out, to
ensure that no pressure is left in the chamber.
b. Measure the distance between the nozzle and where the water lands. Measure the height
of the nozzle above the ground.
c. Repeat a. and b. 2 times to find the maximum distance for the number of pumps.
d. Repeat a. – c. for each trial and complete the data table below.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
With the Students:
4. Data Analysis:
a. Have students create a graph of the maximum distance traveled v. the number of pumps
using the data they recorded in their data table.
b. Have students calculate pressure for each trial.
•
This is very dependent on students’ level of comfort with algebra!
•
Recommended: Go through the sample calculations with students that is provided on
•
If students are not comfortable doing the calculations, use two data points from a
group (for example, 3 pumps and 9 pumps) and work through the calculations as a
class to find the pressure in each case. Discuss the relationship between the number of
pumps, the pressure and the distance the water traveled.
•
Another option: if all groups are using the same type of water gun, assign each group a
trial (number of pumps) and have that group calculate the pressure. Have groups share
results with the class, and then each group can graph the pressure v. the number of
pumps.
c. Discuss results together as a class and re-emphasize the engineering connection
(biomedical engineering, civil engineering).
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
A Shot Under Pressure
Teaching tips:
o Emphasize the science concepts, vocabulary, and engineering connection;
reinforce these throughout the activity.
o As mentioned on the last slide, go through the sample calculations with
students that is provided on the Take Your Best Shot Worksheet Answers.
o Depending on your water gun design, it’s best to place the water gun
sideways on a flat table to ensure a horizontal shot and easy trigger access.
o One or two pumps might not yield any results depending on the type of water
gun used. If this is the case, have students start their data collection at the first
number of pumps that yield results and perform trials at up to ten pumps
beyond that.
o It is important to leave some air in the water tank to make sure the water gun
works properly.
o If holding the trigger until the water stops shooting does not work, the
depressurization of the chamber between trials can be achieved by opening
the water tank, thereby depressurizing the system.
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
Activity Takeaways
• Teambuilding skills
o Working together on experimentation, collecting data, performing
calculations and analyzing results
• Engineering skills
o Engineering Research and Analysis: conducting experimental trial,
gathering results, analyzing data, relating results to real world
engineering (biomedical and civil engineering)
• Encouragement through hands-on
learning
o This activity is very hands-on, and allows
students to use water guns to collect and
analyze data in order to learn about science
and engineering concepts.
• Motivation through having fun
o Introduce the activity as a fun learning
experience!
http://www.buckeyeaz.gov/index.aspx?nid=163
SHPE Foundation
SHPE Jr. Chapter Curriculum
Hands-On Activity Training
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