Walking with coffee why does it spill

When you walk, even though you may only be going in one direction along the floor, there is still a back and forth, or oscillatory, motion to your walk. Walking in and of itself is a complicated motion. The body rotates slightly along the head-to-foot axis, moves a bit up and down with each step, and arms tend to move about the joints shoulder, elbow, wrist. When you walk with a cup full of fluid in your hand your walking motion changes a bit, for example, there is less rotation about all of the arm joints.

Some of the motion energy of walking gets transferred to the cup and to the fluid in the cup. Try it out! Think back to the swing. If you pump your legs at the wrong time the swing does not get any higher.

If you pump them at just the right time dependent on where the swing is located you go higher. It turns out that the coffee cup has similar features. If you input energy at just the right time, you can make the liquid in the cup go higher. It turns out that the combination of the cup dimensions and common walking makes for just the right combination to get spills. Figure 2: Holding cup of coffee showing the x-axis, which is parallel to the floor and the y-axis, which is vertical from the floor.

The z-axis, perpendicular and into and out of the surface of this image was not measured. How do you get data for such an event? Take a video!

Then process the time frames to get the time and location of the coffee and person, as well as the velocities, and accelerations. Krechetnikov and his graduate student Hans Mayer, the primary author of the study, suggested two explanations for this result: First, focusing on one's cup tends to engender slower walking, and second, it dampens the noise, or chaotic sloshing, in the cup.

Whether focused carrying decreases the amount of noise because we perform "targeted suppression," automatically counteracting the sloshing of the liquid with small flicks of our wrists, or because we simply hold the cup more steadily when we're looking at it, the researchers could not say. Third, accelerate gradually.

If you take off suddenly, a huge coffee wave will build up almost instantly, and it will crash over the rim after just a few steps.

But the best way to prevent coffee spilling might be to find an unusual cup. In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup.

These observations are analyzed from the dynamical systems and fluid mechanics viewpoints as well as with the help of a model developed here. Particularities of the common cup sizes, the coffee properties, and the biomechanics of walking proved to be responsible for the spilling phenomenon. The studied problem represents an example of the interplay between the complex motion of a cup, due to the biomechanics of a walking individual, and the low-viscosity-liquid dynamics in it.

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Many researchers now find themselves working away from their institutions and, thus, may have trouble accessing the Physical Review journals. Liquid sloshing engineering studies show that a flexible container act as a sloshing absorber that prevents liquid oscillations. Professor Ying-Cheng Lai, an electrical engineering professor at Arizona State University, said that humans have a natural ability to interact with complex objects but have no understanding of those interactions in a quantitative model.

Humans do not analyze external factors, like the climate or noise, during these interactions, yet it is crucial in applied fields like soft robotics. Brent Wallace, a doctoral student at ASU, said that it plays a significant role in designing smart prosthetics that mimic the flexibility of the natural motion of human limbs. Lai added that in the future, robots could be deployed in different fields for complex object handling and control, which are activities that need coordination and movement control levels similar to humans.

In the study, titled " Synchronous Transition in Complex Object Control ," published in Physical Review Applied, researchers added a rolling ball to the coffee-cup-holding paradigm and let participants rotate the cup in a rhythmic pattern with the ability to change their force and frequency to ensure that the ball remains contained. The team noticed that participants tend to apply low-frequency or high-frequency strategies to handle a complex object.