The Physics of Going Fast—but Not Too Fast—on a Giant Slide

Actually, the one distinction is that this can be a downward-curving path with the middle of this round curve beneath the slide as a substitute of above. (As soon as once more, the grey C-shape represents the trail of the rider on the slide and the round trajectory of their physique, and the dot is the middle of the circle.) Meaning the centripetal acceleration can also be within the downward course and in the direction of the middle of the circle.

For the reason that acceleration switched instructions, the conventional pressure (N) needs to be much less than the radial part of the gravitational pressure, which is pulling the particular person downward towards the Earth. What occurs when the conventional pressure will get smaller?

Keep in mind that with the intention to get a rider to maneuver in a round path, there must be a internet pressure pointing in the direction of the middle of the circle, which is down-ish for a downward-curving slide. For the reason that frictional pressure is all the time tangent to the slide path, this internet radial pressure, which we name the centripetal pressure, consists of the conventional pressure (pushing away) and a part of the gravitational pressure (pulling in the direction of the middle).

If the pace of the rider is gradual sufficient, you don’t want a really massive centripetal pressure to maneuver them in a circle. The part of the gravitational pressure alone might be sufficient to attain it. The traditional pressure from the slide might simply be some small worth pushing away.

If the rider’s pace will get too quick, then the gravitational pressure alone wouldn’t be sufficient to provide round movement. You would wish the conventional pressure to additionally pull towards the middle of the circle. However slides don’t do this: They solely push away. That signifies that the sliding human wouldn’t really transfer in a circle, however as a substitute alongside a parabolic path as they depart the floor of the slide and develop into airborne—not less than for a short while, till they crash again into the slide. That’s what occurred to the Detroit slide riders.

Let’s mannequin the movement of an individual on a downward-curved slide. I will begin with a rider on the prime of a curve. You possibly can see that in some unspecified time in the future the particular person flies off the monitor and turns into a free-falling projectile:

The particular person’s pace as they start their journey is essential. If an individual begins the downward curve with a excessive sufficient pace then they may fly off the monitor—however the actual worth for the pace that can trigger the particular person to come back off the monitor relies on the beginning and ending angle of the slide’s curve.

If you wish to preserve your riders on the slide, you could enhance the coefficient of friction between them and the slide. Ultimately, the Michigan Division of Pure Assets, which runs Belle Isle Park, posted a Fb video explaining the updates they’ve made: “We’ve got scrubbed down the floor and began to spray somewhat water on the slide between rides to assist management the pace,” they wrote. Additionally they urge the riders to lean ahead—which a park worker demonstrates within the video.

Why water? Water is definitely sort of sticky, so simply including somewhat little bit of it might enhance the friction because of its cohesive nature. (After all, including sufficient to create a full-on waterslide would possibly scale back the friction and make the rider even quicker—however that may take a lot extra water.)

Leaning ahead might assist make sure that every rider’s weight is on the material sack on their legs. The sacks are product of burlap, which is scratchy and supplies some friction—and since all of the riders must put on these sacks, that makes for a extra constant, recognized floor than no matter clothes the riders occur to be sporting. Asking them to lean ahead makes certain the burlap is involved with the slide, not the fabric that makes up the particular person’s shirt—which is what would occur in the event that they leaned backwards.

If the park operators wish to get much more inventive, another choice can be to have riders slide whereas sporting one thing aside from these burlap sacks—possibly one thing with somewhat little bit of rubber to extend the friction interplay. It is also potential {that a} coat of paint might enhance the coefficient of friction.

Completely happy sliding!