Centripetal force demonstrator, desktop looping track - CYCLONE
🚚 FREE DELIVERY
Tax included
The Lab Wooden base A marble released at the top of a slope, a moment of suspense, then it climbs, goes upside down at the top of a vertical circle, and comes back down without ever falling. This centripetal force demonstrator reenacts the founding experience of roller coasters right on your desk. Its silhouette consists of a single gesture: a polished metal rail descending a slope, curling into a unique vertical loop, and then shooting toward a small black cap at the end of the course. The whole rests on a dark wooden rectangular base that gives it the look of an instrument from a cabinet of curiosities. Originally designed as educational physics equipment, it speaks as much to the high schooler discovering circular dynamics as it does to the nostalgic engineer or the simply curious. Each launch poses the same question: why doesn't the marble fall when it is upside down? The answer lies in speed, curvature, and a handful of elegant equations that the object suddenly makes tangible. A demonstrative desk object, sober and expressive, that turns a Newton's law into a spectacle of a few seconds.
The model
Centripetal force, or the art of turning without falling
Any object in motion tends to continue its path in a straight line: this is the principle of inertia, formulated by Newton in 1687. For a marble to trace a circle, a force must constantly pull it toward the center: this is the centripetal force, from the Latin centrum (center) and petere (to seek). In the loop, this role is played by the rail itself, which pushes the marble inward, aided at the top by gravity. What one feels on a ride as a push toward the outside, the famous "centrifugal force," is merely the manifestation of this inertia seen from the passenger's seat.
At the highest point, the marble only stays pressed against the rail if it is going fast enough: the square of its speed must exceed the product of gravity and the radius of the loop (v² ≥ g·R). Below this threshold, the rail stops holding it, and it drops. As early as the 1840s, attractions called "centrifugal railways" thrilled the Parisian public with this same principle; the loops of modern amusement parks are their direct heirs.
Why you'll love it
From the fairground ride to the engineer’s desk
There is an almost childlike pleasure in watching a marble defy the fall. 19th-century fairground showmen understood this by installing their first looping circuits, where intrepid passengers went upside down to the cheers of the crowd. Physicists saw in it an ideal demonstration of the link between speed, radius of curvature, and gravity.
This demonstrator takes up this dual lineage. Its unique, clean, and legible loop recalls the engraved plates of mechanics treatises; its dark wood base evokes the demonstration instruments of old science classrooms. On a desk, it becomes a ritual: one releases the marble, holds one's breath, watches it go upside down and return. A little theater of Newtonian mechanics, replayed at will, reminding us that the laws of nature are as beautiful as they are exact.
Staging the loop in four steps
Comparison
| Criteria | This model (one loop) | Single or double loop rail |
|---|---|---|
| Number of loops | One, vertical | One or two depending on version |
| Rail | Metal, polished steel appearance | V-profile aluminum |
| Base | Rectangular dark wood | Wood, length ≈ 40 cm |
| Marble(s) | Metal marble shown | Steel marble and 2.5 cm plastic marble |
| End of course | Small black cap | Marble catch net |
| Dimensions | Not provided | Loop radius ≈ 7 cm (and ≈ 3.5 cm) |
| Ideal usage | Demonstrative desk object | Comparative experiments in class |
Both demonstrators tell the same physics story with different temperaments: this one focuses on the legibility of a single loop, the other on experimentation. To compose a real science corner, browse all of our scientific objects from The Lab.
Good to know: this demonstrator is sourced from physics teaching equipment. Its exact dimensions and weight are not provided by the manufacturer; this sheet sticks to what the product photo shows: a single-loop rail on a dark wood base, presented with a metal marble.
Tip: before each demonstration, wipe the rail and the marble with a dry microfiber cloth. A fingerprint or a grain of dust is enough to slow the marble down and make it miss the summit. A small spirit level placed on the base ensures perfect horizontality.
Technical characteristics
| Type | Centripetal force demonstrator (looping rail) |
| Number of loops | One vertical loop |
| Rail | Metal, shiny polished steel appearance |
| Marble | Metal (shown in product photo) |
| Base | Dark wood, rectangular shape |
| End of course | Small black cap at the end of the rail |
| Operation | Gravity only, no power source |
| Concepts illustrated | Inertia, centripetal force, potential and kinetic energy |
| Usage | Classroom demonstration, desk object |
| Dimensions | Not provided |
| Weight | Not provided |
| Delivery assembled or in kit | Not provided |
Precautions: the marble is a small part that can be swallowed: this demonstrator is not suitable for children under 3 years old and should be used under adult supervision with younger ones. Do not force the rail: a deformed loop will no longer guide the marble correctly. Do not throw the marble by hand off the path.
A gift idea that goes full circle
For a physics teacher at the end of the school year, an engineering student, a mechanics enthusiast, or a colleague who has everything, this demonstrator is a gift that gets noticed and shared. It also accompanies a retirement, a new desk, or a baccalaureate success with a touch of scholarly humor.
To extend the pleasure, pair it with a puzzle or an intriguing desk object from our puzzles and desk objects collection, or explore the other physics and movement experiments from The Lab.
Frequently Asked Questions
Why doesn't the marble fall at the top of the loop?
Because it's going fast enough. At the summit, the marble needs a force directed toward the center to continue turning. As long as its speed is sufficient, gravity alone is not enough to provide this force: the rail must still push it inward, which keeps it pressed against it. If the speed drops below the threshold defined by v² = g·R, gravity becomes "too strong" for the circular trajectory and the marble leaves the rail. This is exactly what ensures passenger safety in an amusement park loop: the entry speed is calculated with a large margin.
Does it need batteries or an electrical power supply?
No. The demonstrator works solely thanks to gravity. The energy the marble needs to travel through the loop is provided by the starting height: by descending the slope, it converts its potential energy into speed, then spends part of this speed to climb back to the top of the circle. No motor, no battery, no cable is involved. This is precisely what makes the experiment so expressive: everything observed stems from the initial height, the shape of the rail, and friction. Simply place the object on a flat surface to be ready for use, at any time.
What is the difference with The Lab’s single or double looping rail?
Both objects illustrate centripetal force, but they are not aimed at the same use. This model focuses on a single loop: its path can be understood at a glance, making it a demonstrative desk object and an excellent starting point for a discussion. The other demonstrator, more laboratory-oriented, offers a version with two loops of different radii, two marbles of different materials, and a catch net, to multiply comparative trials. If you are looking for a sober object to display and have people try, this one is ideal; for a complete practical session, the other will be richer.
What happens if the marble doesn't clear the loop?
That is an experiment in itself. If the marble is released too low on the slope, it does not accumulate enough speed: it climbs into the loop, slows down, then drops before the summit and falls back. In theory, for a marble that slides without friction, you would need to start from a height at least equal to two and a half times the radius of the loop; a marble that rolls must start a little higher, because part of its energy is used to make it spin on itself. Also, check that the base is perfectly horizontal and that the rail is clean: dust or a slight tilt is enough to make a pass fail.
Can it be used in class or with children?
Yes, that is its primary vocation: it is physics teaching equipment. In middle school, it simply illustrates the conversion between height and speed; in high school and higher education, it allows for approaching Newton's second law in circular motion, the concept of support reaction, and the condition for clearing the summit. With young children, the object is fascinating, but it must remain under adult supervision: the marble is a small part that can be swallowed, and the demonstrator is not suitable for those under 3. For older ones, it is a great starting point for asking questions and formulating hypotheses.
What are the dimensions of the demonstrator?
The manufacturer does not provide dimensions or weight for this model, and we prefer not to offer approximate figures. The product photo shows a set composed of a slope, a single vertical loop, and an exit rail fixed to a rectangular dark wood base, with a metal marble and a small black cap at the end of the course. If space is a deciding factor for you, for example for a specific shelf or display case, write to us before your order: we will provide any additional information we have on this object.
How do I maintain the rail and the marble?
Maintenance is minimal. Regularly dust the rail with a dry microfiber cloth, following the entire length of the loop, and wipe the marble in the same way: fingerprints and dust create friction that slows the marble down. Avoid aggressive household products and water on the wooden base, which could stain or swell. Keep the marble near the object, in a small dish for example, so as not to lose it. Finally, handle the demonstrator by the base rather than the loop: it is the precise geometry of the rail that ensures successful passes.
