# Car vs. water jet

Lets say mayor Stu P. D. Tea decides that his main road is ugly and it needs a fountain. He diverts some plumbing, opens a manhole, turns the water on and shazoom - a column of water emerges, roaring high up in the sky.
On the same time a blind, deaf man drives his car on this road at 60 mph. He collides into the water column. What happens next? He keeps on going? Is he sent to hyperspace? Does his car crash just like it’ve hit a telephone pole?

Depends on the size of the water jet. If it’s large enough in diameter and moving fast enough, then yes, there’s enough momentum transfer to counteract gravity. Here’s a video of your exact scenario.

Considering the 60 mph speed, the car would have only momentary contact with the water column. At worst, it would be like a Hal Needham cannon roll.

Needham’s cannon is a vertical welded cylinder in a car. A short section of a telephone pole is placed in the tube, with an explosive charge at the closed end. In the movies, when a moving car flips over, it’s usually done with a Needham cannon. Next time you see a scene like that, you might see the mouth of the cannon on the overturned car.

Anyway, your blind deaf driver won’t go straight up. The water will strike a glancing blow.

nm

if the water is moving fast enough wouldnt it behave as a hard surface? If someone hits water with enoguh speed the unfortunate person will die from the impact. And it will feel like he/she hit a concrete floor.

That’s more a function of the speed the person is moving when they hit the water; in the scenario at hand it might be a problem to a Lamborghini doing 200+mph, but at highway speeds it would at most tear up the plastic bumper cover.

I’ve seen (but can’t find now; ain’t it funny how that always happens?) a youtube video where a low spot in the road and a heavy downpour combine to make the storm drains work in reverse: the water surges and blows off a manhole cover, one car carefully drives through it as it pours up out of the manhole; the flow momentarily stops, and then the water comes back with a vengeance just as the next car plows into it at full speed. Once the pressure subsides, car #2 can be seen stopped just past the spouting manhole with no obvious damage.

The car just floated through it, more or less.

If the pressure is high enough, and the jet small enough, it would slice the car in half.

Now, thats something that Mythbusters should do!

Beat me to the reference, but you missed the obvious extension: that the force of the cannon is proportional to the car’s speed. One of Needham’s wildest accidents came when they misjudged the cannon load, giving it a charge that would roll the car at some slow speed (= a lot of charge), then did the stunt at much higher speed (= one hell of a long roll-out instead of a simple flip).

I’m not quite sure how to assign the factors, but all things considered, hitting a strong jet of water at 60 would be more dangerous and unpredictable than hitting it at 5.

Don’t forget that water jet cutters carry a lot of abrasive grains in the stream, usually garnet.

Blind, deaf driver?

Then I guess we have an answer!

Probably drives by scent. And if the water is clean enough…

Sure. How else would he NOT see the column of roaring water?