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A centimeter-size platelet of dry ice on a hot flat surface (320 °C) with a small weight (m = 0.54 g) on the right side. The added mass tilts the platelet (by an angle θ = 0.3°), so that the ice gets propelled (enhanced online).. Two pictures are separated by 0.3 s and the scale represents 1 cm. The asymmetry can also be made by sculpting the dry ice (enhanced online). [URL: http://dx.doi.org/10.1063/1.4807007.2] [URL: http://dx.doi.org/10.1063/1.4807007.3]doi: 10.1063/1.4807007.2.
(a) Sketch of the experiment: a platelet of dry ice of mass M with an extra weight of mass m on a side hovers above a flat surface. (b) Viscous force and pressure force applied by the vapor flow on the platelet.
Velocity v as a function of time for a given platelet (of mass M = 2.8 g) and different added weights (of respective masses m = 0.21 g, 0.78 g, and 1.24 g). The stronger the added mass, the more accelerated the platelet (enhanced online). [URL: http://dx.doi.org/10.1063/1.4807007.4]doi: 10.1063/1.4807007.4.
(a) Measured angle θ as a function of the added mass m. The solid line represents Eq. (4) , its slope is given by rad/kg. Each point is an average on five measurements. (b) Measured driving force F as a function of the added mass m. The solid line corresponds to Eq. (5) . Each point is an average on ten measurements.
Two platelets of dry ice linked by an off-centered steel rod rotate. Two successive pictures are separated by 200 ms and the bar shows 2 cm. The angular acceleration deduced form these pictures is 2.0 ± 0.1 rad/s2 (enhanced online). [URL: http://dx.doi.org/10.1063/1.4807007.5]doi: 10.1063/1.4807007.5.
A square platelet of camphor (6.0 g) with a small mass of 1.8 g on a hot plate (400 °C). Although the solid is now surrounded by liquid camphor, the whole object still self-propels. Two pictures are separated by 0.65 s and the scale represents 1 cm (enhanced online). [URL: http://dx.doi.org/10.1063/1.4807007.6]doi: 10.1063/1.4807007.6.
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