Science Buddies: "Ask an Expert"

My son needs to build a vehicle that will go two meters without a motor or being pushed by hand.

Congratulations to you on getting involved with your student on what will be a really fun science project.

I was just searching through the ScienceBuddies web site, and I see this is not an uncommon project. I found one inquiry about it going back to 2005. Unfortunately, the web references given in that thread of discussions are no longer valid.

And just a couple months ago, this thread of messages was posted on ScienceBuddies: https://www.sciencebuddies.org/science- ... 77&start=0. Reviewing it won't help you much because there is not much detail in the thread to date, but I just wanted to you to know you're not alone.

I have some recent experience with this type of project. One of the other things I do to help promote science and engineering is to volunteer my time at the local high school to assist with special projects. Just 2 months ago, their honors algebra class did a set of experiments with "gravity cars." Unfortunately, I don't have a photo of one, but they were very simple. I will attempt to describe them to you, and the experiment.

They were built of Legos. An erector set, or other type of modular construction set would work, too. They were just a simple chassis made from a few plate-type parts. They had a solid axle on the front and rear, each with 2 wheels. The wheels were fixed to the axles so as the axle turned, the wheels turned. Each vehicle had a short, simple tower built on it, about 9 inches tall. On top of the tower was a pully. The students wound a string around the center of the rear axle and over the top of the pulley on the tower. Then they hung a weight on the end of the string. They placed the car on the floor, and let go of the weight. The weight pulled the string, which unwound from the rear axle, powering the car.

The cars went as far as 30 feet. The experiment was to learn about several things - like repeating data points. The students ran 3 trials of each of 5 different weights. They made charts showing how far the car went with each of the weights, and then projected how much weight they would have to use to make the car go some distance they didn't actually test.

It was a great experiment that taught them a lot of the principles of scientific investigation, how to record and analyze data, and how to make predictions of the unknown with known facts.

If this sounds like something you'd like to try, I might be able to get a copy of the experiment plan and the student instructions.

Good luck, and have fun.

Ed Neu
Buffalo, MN

Well I'm not sure if this counts as an engine, but have you tried the CO2 configuration. What you do is tape, glue, or whatever is going to make the CO2 capsuls stay on, on to the car. where you can buy the capsuls is at walmart, in the hunting\fishing and outdoor section, near the paintball guns, and airsoft section, or I think you can find them at gander mountain. ask for paintball CO2 capsuls. I hope that helps.







sincerely,
bluefox609

without a motor

For this exercise, what constitutes a motor? If you search "spool motors" you can find some articles on using twisted rubber bands to drive a spool (as in small wooden/plastic part that thread is wound onto for sewing).

pushed by hand

What constitues "pushed" by hand? Think of how a spring loaded plunger is used on pin ball machines to launch a ball. Can you use something spring loaded to start the car in motion and stay within the rules? There are several variations on this theme that involve dropping masses, levers, pulleys, etc that somehow impart some kinetic energy to push the car.

There are several toys that use "inertial motors" where you get a mass rotating that is attached to the drive wheels and then drop the car and it takes off until the rotating kinetic energy is exhausted.