The tires squealed, and the dial started counting the seconds. After a few tests, I ended up clocking a score of 4.04 seconds. That's fast! Actually, it's too fast. Dodge engineers told me that time resulted from way too much tire spin.
The fix? Launch mode. To use it, I pressed the traction control button once (to disable traction) and then a second time (to enable launch control). I pressed down on the clutch, then down on the accelerator, and finally released the clutch to launch. Using this method, the tires didn't spin nearly as much. I clocked a more reasonable time of 5.5 seconds. The app automatically saves the best time unless I do a reset.
So, where does physics come into play? The test is accurate within one-tenth of a second. You're not measuring the inertia or movement of the car, but your ability to clock the fastest time based on tire spin. It's fun, but not designed to work like a drag racing speed track. (A simple method to track actual movement: Use an iPad app like Mobile Science Acceleration.)
As an extra perk, the Performance Pages let you tweak the rpm setting for launch mode--say, 4500 rpm at the high end for a jack-rabbit start, or down to 2500 rpm for a smoother launch on a looser road. You just scroll to the 'RPM' setting and change it with the arrow keys.
Next, I tried the braking test. I clicked up on the arrow key. After hitting 30 mph, the display showed "Ready" to tell me when to brake. I accelerated a bit more and then hit the brakes, firmly but not abruptly. After stopping, the display read 72 feet. Not bad. Performance braking is all about car control, and the Challenger worked famously.
My most interesting physics lesson came with the G-force test, where the app measures the force of acceleration, braking, and left and right cornering. G-force is actually a measure of force on a human body: One G equals 9.8 meters of gravitational force per second squared, at sea level. Now we'd see how much the car could withstand.
After clicking up on the arrow again, I saw the G-force display. It looks like a magic quadrant: four radars with numbers that show the level of force at all times as you drive. (You can also click up once more to see the "peak" G-force ratings, saved until you do a reset, as in the other tests.) In the parking lot, I tried accelerating quickly (clocking 0.96 of G-force), braking quickly (0.65 G-force), and doing some quick corners (peaking at 0.92 G-force).
Aiming for 1.0 G-force, perhaps with puking
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