A golf ball can have a relatively large number of dimples on a surface thereof. A trajectory of the golf ball calculated under conditions of an initial speed of 260 ft/s, a launch angle of 15.0 degrees, and an initial backspin rate of 3000 rpm can satisfy the following mathematical formula:

Amin≥−5.0*Vave−38.98,

wherein A min represents a minimum value (degree) of a vector angle A in the trajectory, and Vave represents an average volume (mm.sup.3) of the dimples. The vector angle A can be calculated by the following mathematical formula:

A=ATAN(Vy/Vx),

wherein Vx represents a horizontal component of a speed of the golf ball, and Vy represents a vertical component of the speed of the golf ball.

A golf ball can have a large number of dimples on a surface thereof. A trajectory of the golf ball can be calculated under conditions of an initial speed of 260 ft/s, a launch angle of 15.0 degrees, and an initial backspin rate of 3000 rpm satisfying the following mathematical formula,

[00001]$\text{Amax}\ge \text{4}\text{.0}\text{*}\text{Vave + 13}\text{.10,}$

wherein Amax represents a maximum value (degree) of a vector angle A in the trajectory, and Vave represents an average volume (mm.sup.3) of the dimples. The vector angle A can be calculated by the mathematical formula

[00002]$\text{A}\text{=}\text{ATAN}\left(\text{Vy}/\text{Vx}\right),$

wherein Vx represents a horizontal component of a speed of the golf ball, and Vy represents a vertical component of the speed of the golf ball.

An object of the present disclosure is to provide a golf ball having an increased spin rate when being hit with an 8-iron while suppressing rise in a spin rate when being hit with a driver. The present disclosure provides a golf ball comprising a spherical core having an inner core and an outer core, and a cover positioned outside the spherical core, wherein A×a is 12,200 or less and B×b is 20,400 or more, where “a” represents an average hardness (Shore C) of a hardness (H2.5) at a point of 2.5 mm from a center of the spherical core and a hardness (H5) at a point of 5 mm from the center of the spherical core, “b” represents an average hardness (Shore C) of a hardness (H7.5) at a point of 7.5 mm from the center of the spherical core and a hardness (H9) at a point of 9 mm from the center of the spherical core, “A” represents an impulse difference (kN.Math..Math.s) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with a driver, and “B” represents an impulse difference (kN.Math..Math.s) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with an 8-iron.

A golf ball 2 includes a main body 4 and a paint layer 6 positioned outside the main body 4. The main body 4 includes a spherical core 8, a mid layer 10 positioned outside the core 8, and a cover 12 positioned outside the mid layer 10. An indentation depth, measured when the paint layer 6 in a cross-section along a plane passing through a central point of the golf ball 2 is pressed by a force of 30 mgf in a direction perpendicular to the cross-section, is not less than 300 nm and not greater than 3000 nm. The paint layer 6 preferably has a thickness of not less than 5 μm and not greater than 50 μm.

An object of the present disclosure is to provide a golf ball which has excellent spin performance on approach shots and from which stain such as mud or grass juice can be wiped off when the golf ball has the stain adhered thereto. The present disclosure provides a golf ball comprising a golf ball body and a paint film composed of at least one layer and formed on a surface of the golf ball body, wherein an outermost layer of the paint film includes, as a base resin, a polyurethane obtained by a reaction between a polyisocyanate composition and a polyol composition, the polyol composition contains, as a polyol component, a polyrotaxane having at least two hydroxyl groups and a urethane polyol, and the outermost layer of the paint film has a tackiness of 0.294 N or more measured with a friction tester under specific conditions:

An apparatus having a control circuit including a computer processor and a computer memory configured with computer software. The control circuit causes a first test assembly to conduct an initial test of the air pressure within an inner chamber of a first tennis ball; and if the control circuit determines that the air pressure is below a threshold, a pressurization process increases the air pressure inside the inner chamber of the first tennis ball by piercing the outer skin of the first tennis ball with a needle, until a tip of the needle is in the inner chamber, and a first opening, plugged by the needle, is formed in the outer skin of the first tennis ball. The needle tip is thereafter withdrawn from the inner chamber of the first tennis ball, leaving the first opening unplugged and sealant is applied to the first opening to close the first opening.

A method and system for determining concentricity of a multiple layer golf ball are disclosed herein. One or more images of a golf ball are generated using an X-ray source, a camera or a digital detector, and an image intensifier. An edge detection algorithm is preferably utilized. The method also includes calculating Y,Z center coordinates of the a best fit diameter or ellipse of the inner edge layer and outer edge layer of the multiple layer golf ball.

A golf ball sorting system has a ball feeder, a ball mover, a detector, and a sorting system. The ball feeder may be configured to receive a plurality of golf balls. The ball mover may be configured to move each of the plurality of golf balls one at a time at a predetermined minimum speed. The detector may be configured to inspect each of the plurality of golf balls moved by the movement mechanism and output a detection result based on the inspection. The sorting system may be configured to receive the detection result and sort the plurality of golf balls based on the detection result to separate golf balls that include a mark that is not visible to an observer from golf balls that do not include a mark.

Systems and methods for measuring the concentricity of golf balls using filter pairs to gather and analyze data on concentricity.

A golf ball 2 includes a main body 4 and a paint layer 6 positioned outside the main body 4. The main body 4 includes a spherical core 8, a mid layer 10 positioned outside the core 8, and a cover 12 positioned outside the mid layer 10. An indentation depth, measured when the paint layer 6 in a cross-section along a plane passing through a central point of the golf ball 2 is pressed by a force of 30 mgf in a direction perpendicular to the cross-section, is not less than 300 nm and not greater than 3000 nm. The paint layer 6 preferably has a thickness of not less than 5 μm and not greater than 50 μm.