Question - I have a '96 Dodge Dakota, and whenever I leave the truck, I get a shock when I touch the door. This is really starting to tick me off. Other than wearing a rubber suit and gloves, what can I do? - Duke
RAY: It's back! Another static-electricity epidemic. There was a static explosion in the mid-1970s, mostly attributable to the proliferation of polyester leisure suits. But the current static-electricity problem seems to have its roots in tires.
TOM: Yes, tires! The tires play a role in grounding the car and diffusing the natural buildup of static electricity. But many of today's tires are so-called "low rolling resistance" tires, which reduce rolling friction in order to improve gas mileage.
RAY: Instead of using a compound called "carbon black" to hold the rubber together, these "low rolling resistance" tires use "silica" as their reinforcing agent. That improves gas mileage, but decreases a tire's ability to diffuse static.
TOM: So under certain conditions - particularly when the air is dry - cars with these tires can deliver significant shocks to unsuspecting, exiting passengers. And if you're driving in a car with low rolling resistance tires on a dry day while wearing a polyester leisure suit, well, you'll probably look like a sign outside a Las Vegas hotel when you grab the door handle.
RAY: Here's what I'd do, Duke. Since the truck is still brand-new, I'd take it back to the dealer and ask if they'll swap the tires for you. Ask them for some nice, gummy, high rolling resistance treads.
TOM: If they won't do that, or if every ounce of gas mileage is important to you, invest in a pair of those static diffusing rubber strips that attach to the truck's frame and hang down and drag along the ground.
RAY: Yeah. I got a pair of those for my wife. Her minivan shocks her every time she gets out and touches the door handle. And as soon as she agrees to stop serving broccoli five times a week, I'm going to install them for her.
Question - The other day, my kids had a helium-filled balloon in the car. Whenever I stepped on the brakes, all the passengers were pushed forward, but the helium filled balloon went backwards. Why is this? - Jeff
TOM: Great question, Jeff. I guess this was one of those laws of physics that Newton never got around to writing.
RAY: The reason the helium-filled balloon goes backwards when you step on the brakes is because everything else in the car - including the air - goes forward.
TOM: According to our buddy Isaac Newton, when your car is in motion and you step on the brakes, your passengers and the air around them "remain in motion" - that is, they go forward. And when the air "goes forward," it pushes the helium (which is lighter than air) out of the way, or toward the back of the car.
RAY: It's the same reason we say "hot air rises." Hot air doesn't actually "rise." Cold air sinks! Cold air is heavier, so it drops down toward the floor and displaces the warmer, lighter air, which gets pushed up to the ceiling.
TOM: The more interesting question, Jeff, is what happens when you suck in the helium, and then - in a helium-induced Mickey Mouse voice - ask an unsuspecting toll-taker to "take me to your leader, earthling."