Page 32 - DESIGN & MODELING

Lesson 3: Cardboard Skimmer

Measurement continued…

Throughout history many systems of measurement have been devised and then thrown out as
more precise and more logical systems have come along. While most of the world has adopted
the metric system, the United States still clings to the Standard system, also called the customary
system. Which system are you more comfortable with? Why do you think that is true? In this
measurement lab, you will have a chance to perfect your precision measuring skills in the system
that you are less comfortable with. STEM professionals, such as scientists, technologists,
mathematicians, and engineers, must be able to measure accurately. It is very important that you
pay attention to the units that you are using.

SCIENCE BACKGROUND CAPSULE

When an object moves through air, the air pushes against it, slowing the object's movement. The
force that slows an object's forward motion is called drag. Drag is a form of friction. One way to
reduce drag is to design an object with a streamlined shape that allows air to flow around it
easily. Streamlined shapes re not pushed back easily by air so they cause less drag. Conversely,
shapes that block the smooth flow of air cause the air to swirl or eddy, around them, causing
drag. In Explore, students attach paper (cut in various shapes) to the front of a toy car and
measure the effects of drag on each. Generally, the larger the shape's surface, the greater the drag
and the shorter the distance the car will travel. In Investigate, students test body designs for their
skimmers to find which shapes make the skimmers more streamlined. While some shapes will
appear to make the skimmer more streamlined, shapes that are too large may add too much
weight to the skimmer and reduce the distance it can travel.

The skimmer functions by using air scoop to create lift. The lift is very slight but is enough to
create less friction under the vehicle. The vehicle moves faster and easier due to the lift. Also,
due to the cardboard construction, the skimmer weighs less and allows the lift to work its magic.
The so called 'wings' stabilize the craft as it moves forward so it doesn't tilt one way over the
other.

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