Bobsled racing is a very technical sport; it combines science and engineering to design the most efficient sled. Through this activity, participants explore concepts such as friction, gravity, and air resistance and their impact on acceleration.

Working individually or in small groups, visitors use recycled materials to design, build, and test their bobsled on our 8-foot long bobsled track. Get a first-hand experience of the design process that scientists and engineers undergo by conceptualizing the problem, designing and testing a prototype, and making modifications as necessary to optimize the solution.

The goal of this challenge is to create a miniature bobsled that is either as fast or as slow as possible. Start with one bobsled base - ours are the trays used to package pipette tips; if you're going this at home, you could use soap dishes.

## Step 1: Choose Materials

Once you have your bobsled base, you can use the other materials provided any way you like. You are the engineer, and you can solve the problem any way you want. The materials we have are:

- Fabric strips, measuring approximately 3 by 8 inches.
- Binder clips
- Dead batteries, for weight (wrapped in purple duct tape)
- Straws
- Pipe cleaners

All of these are simple household materials. Try an arts & crafts store to purchase the fabric, or you could cut up old clothes.

## Step 2: The Rules

There are two rules for this activity.

First, you may use 0, 1, 2, 3, or 4 dead batteries in your design. No more than 4.

Second, no part of the metal binder clips may touch the track. They will scratch the track and make a horrible noise!

## Step 3: Test and Improve

When you are ready to test, bring your design to the test track, decide whether you would like a straight track or one with a hill, and tell the museum educator running the tests which track you would like. He or she will place it on the track and start the test. Make sure you can see your bobsled as it zooms down the track!

Our track times how long it took your bobsled to descend the track and displays it in seconds on a screen on top of the track. Remember that time so you can compare it to your subsequent tests.

Real engineers do not build things perfectly on their first try, so you are allowed as many redesigns and tests as you would like until you are happy with your result. Test your design, make one change, and test it again, keeping track of your time. It is important to change one thing, or "variable," at a time because if you make multiple changes, you won't know which change made your bobsled faster or slower.

To recreate our bobsled track at home, you might try a playground slide and a stopwatch. Alternatively, you could build your own track using a piece of house gutter.

## Step 4: Clean Up

At Design Challenges, we re-use all of our parts, so you may not take your bobsled home. When you take apart your design and put all the pieces back where they belong, we will give you a refrigerator magnet in exchange.

Design Challenges can be found on Level 1 of the Blue Wing at the Museum of Science, Boston. We are open for drop-in participants from 10:30am-12:30pm every day, and in the afternoons on weekends, school vacation, and summer vacation.