A 127-player single-elimination tournament needs a schedule even though its opening bracket is not a neat power of two. Can you work out the number of matches without drawing every round? Look for something each completed match changes, then test whether byes affect the count.
Pedaling a bicycle once around in a low gear moves you a short distance with an easy push; pedaling once in a high gear sends you much farther down the road. The ratio of teeth on the front chainring to the rear sprocket explains how a simple chain drive trades pedaling force against distance traveled.
Drop a basketball onto a still surface and it usually returns to a lower height. Some of the energy available for the rebound has gone into deformation, sound, and heating, rather than disappearing.
On the three-color hexagonal board used in Gliński chess, the bishop still has a color restriction, but now has six diagonal directions. Changing the cells changes what “diagonal” can mean, making a familiar piece a compact puzzle about geometry and movement rules.
A ball can leave a foot headed one way and curve sideways as it travels. Spin changes the airflow around it and can create a sideways force, though the bend depends on more than spin alone.
At six games all, a tennis set can switch to a race for points. A standard tie-break gives the first server one point, then alternates service in pairs. Explore how the serving sequence, two-point winning margin, and changes of ends shape the contest.
Imagine two chess clocks that each offer five seconds per move. One adds time to your balance; another delays the countdown without saving unused seconds. Explore how increment and delay reward quick play differently, even when their allowances look alike.
Your favorite corner of the goal becomes less useful if the goalkeeper knows you always aim there. A penalty kick makes unpredictability a strategic choice, with a balance that depends on each player’s strengths.
Trying especially hard can mean paying attention to movements that normally happen without much conscious control. That is one proposed explanation for a skilled performance faltering under pressure; distraction offers a different one. Golf putting tasks make the distinction concrete, but the explanation may depend on the task and the performer’s experience.
Imagine a volleyball setter and hitter entering a move they have already agreed on. Their positions and timing can make the next action intelligible without a fresh spoken instruction. The interesting boundary is between a shared plan, an observable movement, and a guess about what a teammate intends.
In 2009, FINA announced new swimwear requirements for 2010, including textile construction and limits on suit shape. The interesting question is how a sport decides which improvements belong to the athlete and which should be restricted by equipment rules.
Two fair dice do not give every total an equal chance. A seven can arrive in several different ways, while a twelve has only one route. The surprise comes from counting the outcomes hidden inside a total.