Physics of the Ninja
Lesson Three:
The art of trickery
SCHEDULE
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Introductions and review of class objectives.
Have students form clans.
Presentation of background material.
Perform the Demonstration.
Student teams create a paper shuriken.
Students modify their shuriken for optimal performance.
Students put away materials and clean up.
Students have a shuriken throwing competition.
Background
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One of the most famous tools of trickery is the shuriken or japanese throwing star. Throwing stars come in many different styles
and had anywhere from two to 30 points. These stars were often
thrown into walls before enemies arrived, so that
a person would immediately look at the star. The
ninja could attack from the opposite side of the
room or sneak out the door while the shuriken
was being inspected. They were only sometimes
thrown to damage an assailant.
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Some facts:
• In translational motion, the object in motion stays in motion.
• In rotational motion, a spinning object continues to spin.
• Translational motion is dependent on the applied force and the
mass of the object.
• Rotational motion is dependent on the applied force and where
it is applied to the mass and the distribution of mass. It is the
where that changes the motion! Throwing a shuriken by
twisting the wrist and tossing it by one of its point allows the
star to spin as it moves. It is easier to spin something if it is
thrown at a point farthest away from its axis (center).
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Many people associate weapons with ninjas, but surprisingly
many of the weapons were not used to harm others, they were
used purely as diversion—a tool to fool an enemy into diverting
his/her attention away from the true attack. Modern magicians
are highly skilled at this task and ninjas of the past were often
just as clever and skilled.
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The physics behind a throwing star are easy to understand. For
example, if a Frisbee is thrown across a room, it rotates as it
moves forward. There are two motions, transitional and rotational.
The shape of the thing thrown affects how it moves through the air.
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Demonstration
Take a paper plate and hold it as if it were a shotput or a
baseball. Throw the paper plate overhand and watch it fall to
the floor a few steps away. Ask students what happened. Now
throw the paper plate as if it were a frisbee. Ask students what
changed. Discuss the concept of rotational spin.
master Challenge
Should students finish early have the design a new shuriken
or have them try to skillfully (and carefully) throw a shuriken
around a corner.
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Physics of the Ninja
Lesson Three:
The art of trickery
1. Make your own shuriken
using one piece of paper.
Pencil
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2. Begin with a piece of
notebook paper, with the
longest side at the top.
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3. Take the bottom left-hand
corner and fold it until the
upper left-hand corner is cut
in half.
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Scissors
4. This is how you make a
square.
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Name: _______________________________________ Date: _____________________
Paper
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Physics of the Ninja
Lesson Three:
The art of trickery
6. Fold the square in half and
then cut it in the middle to make
two equal pieces.
8. Flatten each piece as flat
as possible. The openings
should be facing each other.
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7. Fold each of the two pieces in
half horizontally again.
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9. Fold the corners as shown
along the lines shown. Be
sure to fold both sides of
each at once.
10. Make the folds as even
with the top as possible.
Make 90 degree folds
whenever possible.
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Name: _______________________________________ Date: _____________________
5. Cut the non-folded edge off.
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Physics of the Ninja
Lesson Three:
The art of trickery
14. Fold the paper under and
up. Make it a 90 degree fold
so it matches the picture.
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12. Fold the top so it folds under
and makes a 90 degree angle.
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13. Make a fold where the dotted line is shown. You will be
fold the paper under.
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15. Once you have one complete. You will need to make
the second paper exactly
the same as the first. Follow
steps 11-14 to create a second.
16. Set the second paper
piece on the other in the
design shown. The bottom
paper is colored gray for help
with making the star only. The
smooth center should be facing upward.
All materials Copyright ©2012 PCS Edventures, Inc.
Name: _______________________________________ Date: _____________________
11. Take the top paper and turn
it over so the folds are facing
the table. Leave the bottom one
alone for now. Do the next few
steps with the paper this direction.
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Physics of the Ninja
Lesson Three:
The art of trickery
18. Make a fold line on each
of the ends of the papers as
shown.
20. Continue folding the next
two points over the preceding
point. The last point will rest
on top of the center.
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19. Choose one of the corners and fold it into the center.
Following clockwise, fold in the
next point. Be sure to fold it on
the line you created in the last
step. This fold should go on top
of the first.
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21. Take the center and tuck
it under the edge of the previous point.
22. Continue counterclockwise tucking in the point into
the previous fold. It should
hold together on its own, and
the center folds will look like
an X if the star was made
correctly.
All materials Copyright ©2012 PCS Edventures, Inc.
Name: _______________________________________ Date: _____________________
17. If you have trouble you may
color your bottom paper.
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Physics of the Ninja
Lesson Three:
The art of trickery
26. Now throw it as if it were a Frisbee by holding one of the
points. How does it fly? Describe the motion.
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24. Rules of the ninja in training.
• Do not throw the shuriken at
other training ninjas!
• Do not throw the shuriken at
your sensei.
• Always aim low, so you will
not risk hitting someone’s face
accidentally.
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27. Throw the shuriken once again like a Frisbee, only this
time hold it in the center instead by one of the points. Does
it fly well? Does it rotate as much?
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25. Attempt to throw your shuriken safely at a wall or target.
Try throwing it as if you were throwing it overhand but hold it by
one point. What does it do, describe the motion?
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28. Modify your shuriken so
it flies better. Use materials
you have access to in order
to modify it. Test it until it flies
accurately. Remember, a
shuriken is a great diversion!
Place one to divert attention.
All materials Copyright ©2012 PCS Edventures, Inc.
Name: _______________________________________ Date: _____________________
23. You should now have a finished shuriken!
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