A
roly-poly toy,
tilting doll,
tumbler or
wobbly man is a
toyA toy is an object used in play. Toys are usually associated with children and pets, but it is not unusual for adult humans and some non-domesticated animals to play with toys. Many items are manufactured to serve as toys, but goods, or services produced for other purposes can also be used as toys...
that rights itself when pushed over. The bottom of a roly-poly toy is round, roughly a
hemisphereHemisphere may refer to:*Half of a sphereAs half of the Earth:*Any half of the Earth*Eastern Hemisphere*Western Hemisphere*Northern Hemisphere*Southern Hemisphere...
. It has a
center of massThe center of mass of a system of particles is a specific point where, for many purposes, the system behaves as if its mass were concentrated there. The center of mass is a function only of the positions and masses of the particles that compose the system...
below the center of the hemisphere, so that any tilting raises the center. When such a toy is pushed over, it wobbles for a few moments while it seeks the upright orientation, which has an
equilibriumA standard definition of static equilibrium is:This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next....
at the minimum gravitational potential energy.
The toy can represent a person, an animal, or anything else.
A
roly-poly toy,
tilting doll,
tumbler or
wobbly man is a
toyA toy is an object used in play. Toys are usually associated with children and pets, but it is not unusual for adult humans and some non-domesticated animals to play with toys. Many items are manufactured to serve as toys, but goods, or services produced for other purposes can also be used as toys...
that rights itself when pushed over. The bottom of a roly-poly toy is round, roughly a
hemisphereHemisphere may refer to:*Half of a sphereAs half of the Earth:*Any half of the Earth*Eastern Hemisphere*Western Hemisphere*Northern Hemisphere*Southern Hemisphere...
. It has a
center of massThe center of mass of a system of particles is a specific point where, for many purposes, the system behaves as if its mass were concentrated there. The center of mass is a function only of the positions and masses of the particles that compose the system...
below the center of the hemisphere, so that any tilting raises the center. When such a toy is pushed over, it wobbles for a few moments while it seeks the upright orientation, which has an
equilibriumA standard definition of static equilibrium is:This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next....
at the minimum gravitational potential energy.
The toy can represent a person, an animal, or anything else. Different toy manufacturers and different cultures produce different-looking roly-poly toys: the
okiagari-koboshiis a Japanese traditional doll. The toy is made from papier-mâché and is designed so that its weight causes it to return to an upright position if it is knocked over...
and some types of
daruma doll, also known as dharma dolls, are hollow and round Japanese wish dolls with no arms or legs, modeled after Bodhidharma, the founder and first patriarch of Zen. Typical colors are red , yellow, green, and white. The doll has a face with a mustache and beard, but its eyes only contain the color white...
of
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, the nevаlashka or vanka-vstanka of
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
, and Playskool's
WeebleWeebles is a trademark for several lines of children's roly-poly toys originating in Hasbro's Playskool division on July 23, 1971. Shaped like eggs with a weight at the fat, or bottom end, they wobble when pushed, but never fall completely over, hence the name and the slogan "weebles wobble, but...
s.
A toy manufacturer recommends roly-poly toys for small children just developing
motor skillA motor skill is a learned series of movements that combine to produce a smooth, efficient action.* Gross motor skills include lifting one's head, rolling over, sitting up, balancing, crawling, and walking. Gross motor development usually follows a pattern...
s; a child can bat at it without it rolling away.
Most roly-poly toys are hollow, with a weight inside the bottom. A
GömböcA Gömböc is a convex three-dimensional homogeneous body which, when resting on a flat surface, has just one stable and one unstable point of equilibrium. Its existence was conjectured by Russian mathematician Vladimir Arnold in 1995 and proven in 2006 by Hungarian scientists Gábor Domokos and...
is a roly-poly toy made of a uniformly dense material, where only the shape of the top half makes the center of mass below the center of the hemisphere.
Dynamogene Theater stages a performance called Monsieur Culbuto, allowing the audience to interact with a human dressed as a roly-poly toy.