Really, the only difference is that it’s a downward curved path with the center of that circular curve below the slide instead of above it. (Again, the gray C-shape represents the cyclist’s trajectory on the slide and the circular trajectory of his body, and the point is the center of the circle.) This means that the centripetal acceleration is also in the downward direction and towards the center of the circle.
Since the acceleration has changed direction, the normal force (N) must be less than the radial component of the gravitational force, which pulls the person down towards the Earth. What happens when the normal force decreases?
Remember that to get a rider to move in a circular path, there must be a net force pointing toward the center of the circle, which is more downward for a downward curved slide. Since the frictional force is always tangent to the sliding path, this net radial force, which we call the centripetal force, is composed of the normal force (repelling) and a component of the gravitational force (pulling upwards). center).
If the speed of the cyclist is slow enough, you don’t need a very large centripetal force to move them in a circle. The single component of gravitational force could be enough to achieve this. The slide’s normal force can just be a small value that slips away.
If the cyclist’s speed becomes too fast, gravitational force alone will not be enough to produce circular motion. You would need normal strength to too pull towards the center of the circle. But slides don’t do that: they just push back. This means that the gliding human would not actually move in a circle, but rather along a parabolic path as it leaves the surface of the slide and flies away, at least for a short time, until he falls down the slide. That’s what happened to slide riders in Detroit.
Let’s model the movement of a person on a downward curved slide. I’ll start with a runner at the top of a curve. You can see that at some point the person flies off the track and becomes a falling projectile:
Video: Rhett Allain
The speed of the person at the beginning of his journey is important. If a person starts the downward curve with a high enough speed, they will fly off the track, but the exact value of speed that will take the person off the track depends on the start and end angle of the slide curve.
If you want to keep your riders on the slide, you need to increase the coefficient of friction between them and the slide. In the end, the Michigan Department of Natural Resources, which manages Belle Isle Park, posted a video on Facebook explaining the updates they’ve made: “We’ve cleaned the surface and started spraying a little water on the slide between rides to help control the speed,” they wrote. They also urge runners to lean forward, which a park employee demonstrates in the video.
Why water? Water is actually a little sticky, so just adding a little could increase friction due to its cohesive nature. (Of course, adding enough to create a full waterslide might reduce friction and make the rider even faster, but that would take time. plot more water.)
Leaning forward could help ensure that each rider’s weight rests on the fabric bag on their legs. The sacks are made of hessian, which is rough and provides some friction – and because all runners must wear these sacks, it gives a more cohesive and known surface than any clothing runners wear. Asking them to lean forward ensures that the burlap is in contact with the zipper, not the material that makes up the person’s shirt, which would happen if they lean back.
If park operators want to get even more creative, another option would be to slide riders around while wearing something other than those burlap sacks, maybe something with a bit of rubber to increase the frictional interaction . It is also possible that a coat of paint increases the coefficient of friction.
Good glide!