Saturday, September 23, 2006

HotWheels Radar Gun Take Two

A couple of weeks ago I blogged about the Hot Wheels Radar Gun. When I looked through my traffic for the last week (using Google Analytics) I saw "Hot Wheels Radar Gun" pop up as the most common search terms leading readers to my blog. So I decided I should probably conclude my testing to determine if it works.

After my last installment I had the feeling that it worked for constant velocity. I have confirmed that it works surprisingly well. I still need to experiment with accelerating objects though.

Experiment #3: Velocity of a constant velocity car

I experimentally determined the speed of my constant velocity car by timing it over a distance of two meters. I arrived at an average velocity of 0.157 m/s after three trials. With the radar gun set to scale speed (1/64) and kph I was able to get a reading of 35. Every time I did it I got 35 exactly. This converts to an actual speed of 0.15 m/s. If I use the 0.157 as the expected value I arrive at a percent error of 4.5%. I think that's Great!!!

Experiment #4: Real Velocity

Fresh off the constant velocity car I decided to try a real car. So I drove around the empty parking lot at my school and shot the light posts as I went by. I got the same reading as my speedometer every time.

Updated Conclusion:

The Hot Wheels Radar Gun works!!! At least for relatively constant velocity objects. I still need to determine how accurately it will measure velocity on an accelerating body.

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Anonymous said...

What a very cool experiment! I always enjoy seeing how people incorporate the study of physics or other subjects into real-world applications that students can readily relate to. Excellent stuff here!!

Steve said...

Thanks for your kind words. My students love when I bring in toys to explain physics, so I do it every chance I get.

Anonymous said...

I just started teaching high school physics this year and have been trying to figure out a way to teach acceleration kinesthetically but it's difficult as I have no equipment. Did you try using the gun to determine acceleration yet? My school has no money to buy any type of sensors, so I was thinking of purchasing the gun myself but only if it's good for acceleration.

Steve said...

Every time I've done anything involving acceleration I don't get the right answer. It seems to have a slow reaction time.

You might try something else I've done. I'll try to post video instructions this week, but for now check out:

The links include directions for a $5 photogate you can use for acceleration.