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Whelmer #9: Nickel Karate
 Description:
A spatula is used to eject the bottom coin from a tall stack of coins.
Science process skills:
- observation
Complex reasoning strategies:
- deduction
- composing
Standards:
K-4:
- Employ simple equipment and tools to gather data and extend the senses
(Standard A.1.3).
- The position of an object can be described by locating it relative
to another object or the background (Standard B.2.1).
- An object's motion can be described by tracing and measuring its position
over time (Standard B.2.2).
- The position and motion of objects can be changed by pushing or pulling.
The size of the change is related to the strength of the push or pull
(Standard B.2.3).
5-8:
- The motion of an object can be described by locating it relative to
another object or the background (Standard B.2.1).
- An object that is not being subjected to a force will continue to
move at a constant speed and in a straight line (Standard B.2.2).
- Unbalanced forces will cause changes in the speed or direction of
an object's motion (Standard B.2.3).
9-12:
- Objects change their motion only when a net force is applied (Standard
B.4.1).
- Gravitation is a universal force that each mass exerts on any other
mass (Standard B.4.2).
Above Standards from the National
Science Education Standards.
Content topics:
- inertia
- friction
You will need:
- 10 to 12 nickels, quarters or metal washers
- spatula or thin butter knife
- smooth table top
Instructions:
Place the stack of coins near the edge of a smooth topped table or other
smooth surface. Hold the spatula blade flat against the smooth surface.
With a quick flick of the wrist, slide the edge of the blade toward the
bottom coin in the stack. The bottom coin is ejected from stack. The stack
of coins drops without tipping over.
The process can be repeated, making the stack of coins progressively shorter.
With practice the spatula can be slid back and forth very rapidly as coins
are knocked out from under the stack. You may want to place "coin catchers"
at the ends of the table.
Presentation:
This activity creates much excitement in the classroom, especially as coins
or washers begin to fly around the room. You should make provisions for
safety if you use this as a student activity.
Allow students to discover the role friction plays in this activity. Direct
them to experiment with the minimum "flick rate" required to overcome
the effect of friction. If they slide the blade too slowly, friction will
cause the upper coins to tumble over.
Students can use different combinations of coins, washers, game tokens,
spatulas, rulers, to create their own version of this activity.
Content:
This a classic inertia demonstration. It demonstrates the first of Isaac
Newton's Three Laws of Motion, published in 1687: A body remains at rest
or, if already in motion, remains in uniform motion with constant speed
in a straight line, unless it is acted on by an unbalanced external force.
This principle of inertia was Newton's explanation of the "laziness"
of an object, its apparent unwillingness to change unless acted upon. The
term inertia is from the Latin term meaning idleness.
The spatula provides the external force which overcomes the bottom coin's
tendency to stay at rest. It is friction and air resistance which cause
the coin in motion to come to rest.
Assessment:
Type: groups of 2-3 students.
Content/Process: inertia and friction.
Age/Level: all.
Challenge students to create another way to illustrate inertia. As they
demonstrate it to the class, assess them on their understanding of inertia
and friction in describing what they have created.
Notes:
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