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a ball bearing is a type of rolling-element bearing which uses balls to maintain the separation between the moving parts of the bearing.

Ball Bearing

a ball bearing is a type of rolling-element bearing which uses balls to maintain the separation between…

A pair of hands forming a long section of rolled clay into a container.

Modeling a clay container

A pair of hands forming a long section of rolled clay into a container.

A pair of hands smoothing a clay container formed by curling large sections of rolled clay together.

Smoothing a clay container

A pair of hands smoothing a clay container formed by curling large sections of rolled clay together.

"In geometry, a curve generated by the motion of a point on the circumference of a circle which rolls upon the convex side of a fixed circle." -Whitney, 1911

Epicycloid

"In geometry, a curve generated by the motion of a point on the circumference of a circle which rolls…

A pair of hands rolling clay into a cylindrical shape.

hands molding clay

A pair of hands rolling clay into a cylindrical shape.

An illustration of a group of men rolling barrels of flour down a steep enbankment

Men rolling Barrels

An illustration of a group of men rolling barrels of flour down a steep enbankment

A roller. Crushes clods and packs the surface so as to keep the seed moist at the expense of increased evaporation.

Roller

A roller. Crushes clods and packs the surface so as to keep the seed moist at the expense of increased…

"A contrivance for enabling a person to glide swiftly on ice, consisting of a steel runner fixed either to a wooden sole provided with straps and buckles, or to a light iron or steel framework having adjustable clamps or other means of attachment to a shoe or boot. C is a roller skate in which a plate with rollers replaces the runner." — Whitney, 1889

Roller Skate - Side View

"A contrivance for enabling a person to glide swiftly on ice, consisting of a steel runner fixed either…

Spiral with lines AB and CD drawn on piece of paper and rolled into a cylinder to form spiral running from A to D.

Spiral Drawn on Piece of Paper and Rolled

Spiral with lines AB and CD drawn on piece of paper and rolled into a cylinder to form spiral running…

A cylinder of wood, plastic, cardboard, or other material on which wire, thread, or string is wound.

Rack Spool

A cylinder of wood, plastic, cardboard, or other material on which wire, thread, or string is wound.

"Reading a Volumen, or Roll." — Quackenbos, 1882

Volumen

"Reading a Volumen, or Roll." — Quackenbos, 1882