The Physics Of Flintstones-Style Braking

By on August 27, 2011

This is the kind of video that might suffice as standalone weekend entertainment. After all, braking a truck with your feet is a pretty demonstrably bad idea. But the lovable nerds at Popular Science just had to take it a step further and work out the physics of trying to halt a truck ala Fred Flintstone, noting

Let’s estimate he can push down with a force about a quarter of his weight. If he weighs 200 pounds, this would result in a force of 50 pounds, or 225 N. We also know that the force of friction (F) between his feet and the asphalt depends on the force with which he pushes down (N) and the “coefficient of kinetic friction”(μ) between the soles of his shoes, which we will assume are made of rubber, and the pavement.

F = μN

The μ between rubber and asphalt varies between 0.5 and 0.8. Let’s assume a value of 0.7. Therefore, solving for stopping distance, we get:

D = ½(2100kg)(18m/s)2/(0.7)(225N) = 2160 meters, or over 1.3 miles!

The situation might be improved if he exerted his full 200 pounds, or 900 Newtons, of force against the ground. In that case:

D = 1/2(2100kg)(18m/s)2/(0.7)(900N) = 540 meters (about a third of a mile)

However, the amount of torque exerted on his ankles and knees might make that a problematic proposition.

Surf on over to PopSci for the entire breakdown (no pun intended).

19 Comments on “The Physics Of Flintstones-Style Braking...”

• eldo500

If this nimrod crashed into me while pulling that stunt, I’d go straight for the trunk to grab my tire iron and proceed to bash his brains into oatmeal. Not as a result of anger, mind you — I’d just want to make sure he was removed from the gene pool ASAP.

• eldo500

As soon as I hit “submit comment,” I remembered that I drove my VW Bug using only the E-brake to stop for half of my junior year of high school because, ya know, it’s really expensive and complicated to replace wheel cylinders and brake shoes on VW Bugs.

BRB, gonna go check into getting a vasectomy.

• mazder3

Don’t bash his head in. That gets messy. Blood and brain matter all over you and your tire iron. Icky.

It’s far easier and less messy to do what Cartman does, kick him right square in the nuts! Just make sure you are wearing steel-toed boots. Then give him a good stomp once he’s down. Problem solved! :p

• Robert.Walter

“BRB, gonna go check into getting a vasectomy.”

Don’t forget to check to see if you are elligiblefor that blender lottery.

• Bryce

+1

• AthensSlim

Was anybody else thinking that it might have been a good idea for the cop to pull in front of this guy and use his cruiser to stop the truck before he got to the 2nd intersection and potentially killed someone?

• MBella

What you are suggesting is that the cop should use his brain. That is something very unusual in the world of suburban Detroit police. The whole time he was probably puzzled because the guy wasn’t speeding, and he didn’t know what to do.

• gmichaelj

Absolutely – very poor judgement on the part of the cop. No value-added: he should be counseled at a minimum.

• mazder3

Flipping idjit! I’ve had three Chevy trucks blow their brake lines (two owned by my boss, one mine) while having a trailer on and I got home safely. Use the farthest to the left pedal while holding the release open. Pump it. Shift to lower gears. You stop.

• SimonAlberta

Complete lunatic. If your brakes fail and you MUST keep driving surely you go in low gear and slow to a crawl. He surely must have been high or spaced out. Not even a moron is that stupid while sober. Surely?

• Zackman

How this knucklehead avoided hitting anyone is beside me. If he was smart, the truck, as beat up as it appeared to be, should have a hole rusted through the floor and he could’ve used BOTH feet. If he did that, he would’ve stopped, no problem. Must’ve been Barney and not Fred!

Reminds me of another physics problems – what must the velocity of a human body be, in order to completely evaporate upon ideally inelastic impact with a wall that, for simplicity, has zero specific heat?

The answer is a surprisingly attainable velocity.

• Robert.Walter

I’m surprised his feet didn’t catch some kind of crack or joint in the pavement and get snapped off.

What an incredibly stupid person and a real danger to society. With that lack of judgement, he needs to lose his license.

• Sinistermisterman

I only ever lost my brakes once when a rear brake cylinder blew on crappy old K car. I managed to creep home avoiding going down hill, using low gears, the parking brake and occasionally jamming it into reverse when I REALLY had to stop. This guy is a tool.

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