Spool Racer Lab
Engineering Connection
Engineers design motor vehicles to ensure safe and effective transportation. The key component of a motor vehicle is its engine, which serves as the "black box," converting chemical energy stored in gasoline into the kinetic energy of a moving car. Since energy conversion can take place between all different types of energy, fossil fuels are not the only kind of energy input engineers choose for their vehicle designs. For example, some vehicles use batteries to store electrical energy, which is converted into kinetic energy. In this activity, students play the role of mechanical engineers as they design spool racers that demonstrate how elastic energy stored in stretched rubber bands may be used to power spool-wheeled "cars," and experience how different design criteria affect the functionality of their spool racers.
Explore how elastic potential energy from twisted rubber bands can roll spools.
Materials List
Each student needs:
wooden spool (from spools of thread)
rubber band
washer
toothpick
tape
pencil
Introduction/Motivation
In the "What Is Energy?" lesson, we discussed that energy is the ability to make things happen. For example, energy is required to provide heat to the classroom when it is cold outside, and energy in the form of food supports our daily activities such as thinking and exercising. We know that energy can be neither created nor destroyed, so to obtain the energy we need, it must be converted from one form to another. For example, the thermal energy we feel from a heater is converted from some other form, such as the chemical energy stored in fossil fuels (such as when we burn natural gas) or electrical energy. Similarly, a motor vehicle converts some type of stored energy, such as gasoline, into movement, or kinetic energy.
The engines in vehicles, such as cars, airplanes and boats, make the energy conversion happen. Typically, engines consume gasoline to power the motion of vehicles such as cars and buses. Gasoline, which contains chemical energy in a highly compact form, is ignited in a closed chamber, producing a powerful, expanding gas that pushes pistons in a circular motion. A vehicle is moved forward or backward by transferring this circular motion into a linear motion through a crankshaft that connects the pistons to the wheels.
However, gasoline is not the only source of energy that can be converted to move vehicles. Many researchers are inventing, testing and creating vehicles that use new types of stored (potential) energy as alternatives to fossil fuels (which have a limited supply on Earth) to power our vehicles. For example, Tesla Motors uses lithium-ion battery packs to power their electric vehicles, so their cars do not need gasoline. Can you think of another type of potential energy that can be used to move an object?
No matter what kind of engine or battery a vehicle uses, these components must be well engineered to ensure they are safe, functional and reliable for people to use. In this activity, we will explore specifically how elastic energy—which is one kind of potential energy—can be converted into kinetic energy to spin a spool. You will play the role of mechanical engineers to improve your spool racer designs to meet certain design criteria.
Directions:
First:
Pinch and push the rubber band through the hole of the spool. It helps to use a toothpick or pencil to push it through.
Secure the rubber band at one end of the spool by inserting a toothpick into the rubber band loop that sticks out of the spool hole and taping the toothpick and rubber band loop to the spool. Break off any length of the toothpick that is wider than the spool diameter.
On the other side of the spool, pinch and push the other end of the rubber band through a washer. Then slide a pencil through the rubber band loop that sticks out from the washer.
Holding the spool in one hand, use your other hand to move the pencil around the spool two times, so it winds up the rubber band inside the spool.
Set the spool and pencil down on a counter or floor and let go. Watch the spool racer go!
Then:
Modify the design of your basic spool racer to meet the following three criteria—one criterion per trial
Criterion A: Make the spool racer run as fast as possible.
Criterion B: Make the spool racer run as far as possible in a straight line without overturning.
Graded Assignment:
Directions: There is a worksheet provided in Google Classroom. Each member of your group needs to fill it one out and submit it for credit.
