Super Secret Science Challenge SIX: Sleds

Can you design two sleds -- one fast and one slow -- to deliver our Secret Agents to the lair of the evil Mr. Fluffly? You'll need to balance the effects of gravity and friction to make your design work. Join in the engineering fun with this installment of the Super Secret Science Challenge!

This week's suggested supplies:

• 2 cardboard or plastic trays
• 2 drinking straws
• 2 bamboo skewers
• 2 pencil
• 2 pipe cleaners
• 4 binder clips
• 4 paperclips
• 1 piece of copy paper
• 1 piece of wax paper
• 1 piece of plastic sheeting
• 1 piece of cotton fabric
• 4 old AA or AAA batteries
• Assorted tapes -- invisible, masking, duct, packing, etc. 
• A small toy to act as the pilot
• A wood plank, plastic rain gutter, or other material to act as the track

For this week's challenge, students will need to play with the balance between the force of gravity (and weight) on the sled and the friction between the sled and the track. The position of the pilot and any ballast (like the batteries or binder clips) can make for a great discussion about the center of gravity. 

Meanwhile, the decision between using a flat bottomed design, versus one with runners leads to an excellent discussion about how friction works. (The more contact, the more friction.) Additionally, the materials selected for the bottom of the sled (or even for a parachute behind it) can greatly affect how fast the sled moves on the track.

You can use anything you want as a track, but make sure the starting point and end point are clearly defined. The angle of the track will greatly affect the way the sleds run, as will any curves or bends. This can be fun for experimentation.

Good luck agents!