Know what
moves it.

The tip delivers an impulse: force accumulated over its short contact with the ball. That changes the ball’s momentum. An off-center impulse also changes angular momentum, so one strike can create travel and spin together.

The turning effect depends on the perpendicular distance between the ball’s center and the line of force. At a fixed offset, increasing cue speed generally increases both travel and rotation. It does not independently select a new spin-to-speed ratio. Follow-through helps deliver the stroke; after separation, the cue is no longer pushing the ball.

Cue speed, ball speed, and peak contact force are different quantities. A force estimate also needs the contact-time history. In the 3D lab, strength is a cue-speed input and the model computes impulse; the control is not a force meter.

A ball can travel forward while its surface slides over the cloth. Natural roll begins when forward motion and forward rotation match: v = Rω. Here v is center speed, R is ball radius, and ω is forward angular speed. A ball may also carry sidespin while rolling forward.

Sliding friction acts against the relative motion at the cloth contact. It changes both speed and rotation until the bottom point stops sliding. For a center-hit ball with initially zero spin, that usually means less forward speed and more forward rotation. With overspin, friction can increase center speed while total mechanical energy falls.

This is why a low strike can arrive with backspin, with no forward/back rotation, or already rolling: distance and travel time matter. Stun describes the forward/back spin at object-ball contact. It is not the name of one permanent tip position.

For equal masses, a stationary object ball, and an elastic frictionless cut collision, the outgoing velocity vectors are perpendicular when both are nonzero. That is the basis of the 90-degree stun reference. It is a conditional geometric result, not a rule for every pair of real paths.

The normal impulse acts along the line of centers. Tangential contact friction can change the object ball’s direction and rotation. Throw changes the object-ball line; transferred sidespin can affect its later bank. A higher-friction contact can produce an unusual result often called skid or cling.

The cue ball’s remaining rotation continues to interact with the cloth after impact. Draw and follow therefore change its later route even when the initial collision is brief. Separate the departure just after contact from the path a few inches later.

Squirt is the cue ball’s initial deflection away from the cue line on an off-center strike. Swerve is curvature during travel, associated with a tilted spin axis and cloth friction. Throw is a change to the object ball’s direction during ball-to-ball contact.

These effects can partly oppose one another. A shot that happens to finish on the intended line does not prove that none occurred. In an ideal level, point-contact cloth model, pure vertical-axis sidespin alone does not supply a sideways steering force.

For practice, keep the cue close to level and compare small sidespin offsets at a fixed distance and pace. Treat a long-shot miss as a combined observation until launch direction, curvature, and contact have been separated. The 3D lab accepts a supplied deflection angle; it does not infer your shaft’s behavior from its label.

A cushion’s normal force pushes the ball back into the table; tangential friction couples motion along the cushion with rotation. The nose meets the ball above its equator, so top/bottom rotation can matter too. An object-ball collision has different geometry and a second moving ball.

Angle in equals angle out is an ideal mirror reference. Define both angles from the cushion normal before comparing them. In practice, speed, rubber response, contact height, cloth, and spin alter the result. Running and reverse name spin relative to the actual approach; left or right alone does not identify them.

A rebound can have more center speed than before while total energy decreases, because rotation can feed translation. That is not free energy. A kick follows the cue ball; a bank follows the object ball and whatever spin it acquired. Calibrate the relevant ball and route.

Keep starting positions, aim, pace, balls, and table conditions as consistent as practical. State the prediction first. Repeat each condition several times and keep the ordinary attempts as well as the best one. A pattern tells you more than a single impressive finish.

For video measurements, use known distances in the ball-center plane and the actual frame rate. An overhead view reduces perspective trouble. Center tracking estimates travel; a striped or marked training ball helps reveal rotation. Ordinary slow motion may show the later route while missing the brief tip or ball contact.

Treat fitted friction and rebound constants as descriptions of a particular setup and model. Changing the cloth, balls, cue, pace, or measurement method can change the fit. Our 3D lab uses nominal settings and remains a place to form predictions; measured agreement is a separate check.