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New Cars: Adding Features, Adding Weight

The car you have now is probably heavier than the one you had before that. What does that do to the physics of driving and how do modern cars compare to the old steel cars of the past?

These are love taps with a rubber mallet on the thick steel fenders of a 1969 American Motors Rebel, an economy mid-size car of its day 52 years ago, and on a 2021 Lexus ES250 all-wheel drive’s fenders, which thump like a thin skin. 


Lexus loaned us their modern sedan that runs at the cheaper end of their lineup.

So which weighs more? The steel chrome-bumpered Rebel, or the plastic high-tech ES? Don’t answer yet, because the ES comes with all-wheel drive.


The Rebel has a three-speed manual, the ES an eight-speed automatic.

A.M. Radio vs. 10-speakers connected video screen.

Manual steering vs. power that will steer itself back into your lane.

Manual brakes vs. power antilock brakes that stop for pedestrians. 

Cooled power memory seats, power sunshade, and more.


If you’re done guessing, the old AMC weighs 3,172 pounds, the new Lexus 608 pounds more. That’s like six burlap sacks of potatoes in the trunk of the ES, which wouldn’t fit, but it does open and close by itself, adding a few more pounds.


This seemed like basic physics, so we took our questions to Mark Cowley’s Green Canyon High School AP Physics class.


“We look at the motion of objects,” Cowley said. “Not only moving like right to left, but we also look at falling objects within a gravitational field.”


“An object motion stays in motion acted upon by another forest,” said one of the students, Lauren.

We asked Lauren which car takes more energy to get moving.


“The one with more weight, which is the Lexus,” she said. “Because you have to exert more force on it because it weighs more.”


“Anytime an object has more weight it will take more energy to stop, to start going, to accelerate, and to turn,” said Aaron, who didn’t have to stretch for that.


“This is definitely first week’s stuff,” he added.


“Every ounce that you’re adding to that car is going to take a longer to speed up and take longer to slow down,” Cowley said.


But the ES completely outperforms the Rebel.


“Even though there is that trade-off between more weight there may be more safety features but were getting more efficient at the motor being able to convert that fuel from thermal into mechanical,” Cowley said.


But what if we could get the Lexus’ modern engineering with less weight? That would be the Toyota Avalon the ES is based on, at 210 pounds lighter. And it would create some questions for the marketing students.


Brian Champagne grew up in the less-famous Central California but left after starting his television news career there. He worked 22 years in news for NBC, ABC, Fox, and CBS affiliates in four markets. He served as chief photographer for KTXL-TV in Sacramento, but worked in front of the camera, too.