How Does a Basketball Bounce? Air Pressure Science

How does a basketball bounce? When it strikes the floor, the collision’s springiness determines how much it rebounds, measured by the coefficient of restitution, or COR. For a ball dropped from rest, COR equals the square root of rebound height divided by drop height.

FIBA’s cited rebound test drops a basketball from 1800 mm and requires a rebound of 1035 to 1085 mm, equal to a COR of 0.758 to 0.776. NBA-approved balls must have pressure between 7½ and 8½ pounds.

How Does a Basketball Bounce Reveal Elasticity

A basketball bounce begins when the ball hits the floor and rebounds upward, showing that the impact has a measurable degree of elasticity. Rather than returning to its release height, a real ball can rise to a lower height, a result that reveals the collision is not perfectly elastic.

That change in height gives the bounce a result that can be measured instead of merely described as high or low. For this drop, friction can be neglected. Seen this way, the bounce records what happened in a collision between the ball and the surface.

During impact, collision analysis considers motion before and after contact, including momentum and relative velocity. When the second object starts at rest, momentum conservation is expressed as m1v1 = m1v’1 + m2v’2. In an OpenStax elastic-collision example, the first object’s final velocity is -3.00 m/s, with the negative sign indicating a backward bounce.

Basketball’s upward rebound similarly shows a reversal of direction after contact with the floor. Unlike a perfectly elastic case, however, a bounce may not preserve all kinetic energy. Such differences help explain why a rebound can be visible without matching the original drop.

Coefficient of restitution, or COR, gives that measurement a standard numerical form. Defined as the absolute value of relative velocity of separation after collision divided by relative velocity of approach before collision, COR describes how a collision rebounds. For this drop, it relates the two heights.

Because the relationship uses a square root, height ratios and COR values are not the same number. Consequently, a COR between 0 and 1 describes a collision with rebound but less than perfect elasticity. Height therefore supplies a practical observable result, while COR expresses that result as a comparison of the two motions.

Values of e = 1 describe a perfectly elastic collision, with rebound and no loss of kinetic energy. By contrast, e = 0 describes a perfectly inelastic collision, with no rebound and the objects ending up touching.

Neither result matches an ordinary basketball rebound, which rises after impact but does not return to full height. Together, rebound height and COR show both the direction of the ball after contact and the extent of its bounce. That distinction keeps the meaning of a rebound clear.

Energy and Momentum at Impact

During that collision, momentum and kinetic energy provide a framework for describing what changes and what is conserved.

Physics treats a collision as an interaction between objects. When a second object begins at rest, its velocity is v2 = 0.

Here, the primed terms identify velocities after the collision, while unprimed terms identify velocities before it. That equation accounts for momentum shared across the two-object system.

Momentum as a Collision Model

Momentum conservation does not require the first object to continue in its original direction. Depending on the velocities after impact, it can move backward, as shown by a negative result in a worked example. The equation captures both momentum transfer and a reversal of direction without relying on kinetic energy alone to describe the event.

In an elastic collision, both momentum and internal kinetic energy are conserved. Internal kinetic energy means the sum of the kinetic energies of the objects in the system.

Perfect elasticity is an ideal condition for ordinary-scale objects, since truly elastic collisions can be achieved only with subatomic particles, including electrons striking nuclei. Accordingly, a basketball-floor impact does not meet the standard of a truly elastic collision. Its upward rebound still shows that the encounter is not perfectly inelastic.

One OpenStax worked example illustrates how the mathematics can signal a rebound. After discarding a quadratic solution that merely duplicates the initial condition, the remaining solution gives v’1 = -3.00 m/s.

Negative velocity in that setup means the first object bounces backward. Before and after the interaction, internal kinetic energy equals 4.00 J, and total momentum remains conserved. Those equal values describe the example’s elastic collision rather than an ordinary basketball impact.

Classroom experiments can vary the number of discs, their masses, initial conditions, and elasticity to observe momentum and kinetic-energy conservation. PhET’s Collision Lab simulation addresses conservation of energy, collisions, and elasticity. Related simulations are listed under titles including Elastic Collisions, Inelastic Collisions, and Elasticity.

Such comparisons separate ideal conservation rules from the partial rebound seen when a basketball contacts the floor. Rather than supplying a detailed basketball result, the listed simulation description identifies its topics as conservation of energy, collisions, and elasticity. No detailed settings are supplied.

Measuring Bounce with Coefficient of Restitution

Coefficient of restitution, or COR, turns a basketball bounce into a numerical measure by comparing rebound height with drop height. For a ball dropped from rest onto a horizontal surface where friction can be neglected, e equals the square root of h divided by H, where h is rebound height and H is drop height.

From Heights to a Number

When the two heights are known, the calculation follows a short sequence:

1. Measure the vertical drop height, H, from the release point to the floor.
2. Record the rebound height, h, reached after the ball contacts the surface.
3. Divide the rebound height by the original drop height.
4. Calculate the square root of that height ratio to find e.

A result closer to 1 indicates a more elastic collision and a higher rebound relative to the original drop. At e = 1, the collision is perfectly elastic, meaning the object rebounds without a loss of kinetic energy.

Zero represents a perfectly inelastic collision, in which there is no rebound and the objects end up touching. COR is usually a positive real number from 0 to 1. Most real-world collisions have a COR between 0 and 1.

Using the FIBA Rebound Benchmark

FIBA’s cited rebound test provides a basketball-specific example of the measurement. FIBA requires a basketball dropped from 1800 mm, or 1.8 meters, to rebound between 1035 mm and 1085 mm. Those heights equal roughly 57.5% to 60.3% of the original drop height before the square-root calculation. By applying the COR equation, that range becomes 0.758 to 0.776. A basketball that meets the stated rebound range therefore returns well below its release height while still showing substantial springiness.

Because the rebound height is smaller than the drop height, the resulting COR remains below 1. Rather than treating bounce as a simple yes-or-no result, the coefficient supplies a consistent number for comparing the height before impact with the height after it.

Consequently, a larger e value means the rebound height is closer to the drop height under the stated conditions. Only the measured heights are needed for the calculation. NBA rules separately require an officially approved ball pressure between 7½ and 8½ pounds.

What FIBA Rebound Standards Show

FIBA’s cited standard defines the basketball rebound requirement. That required range corresponds to a coefficient of restitution from 0.758 to 0.776, placing the rebound well below the original drop height.

Measured rebound height offers a practical way to compare how different balls and equipment return energy after impact. Basketball’s specified range can be set beside table tennis ball requirements and cited golf-driver COR figures, although each benchmark uses its own test conditions and equipment.

Rebound Benchmarks at a Glance

Item or Equipment	Test or Benchmark	Required or Cited Result	Implied or Cited COR
Basketball	Dropped from 1800 mm	Rebounds 1035-1085 mm	0.758-0.776
Table tennis ball	Dropped from 30.5 cm onto a steel block	Rebounds 24-26 cm	0.887-0.923
Golf-club driver	USGA cited upper limit	Upper COR limit of 0.83	0.83
Golf-club driver	Cited driver-speed range	90 mph to 130 mph	0.845 at 90 mph; 0.797 at 130 mph

Table tennis balls have a higher implied COR range than the basketball standard, from 0.887 to 0.923 compared with 0.758 to 0.776. Golf-driver figures also sit above the basketball range: the cited USGA upper limit is 0.83, while the listed driver values run from 0.845 at 90 mph to 0.797 at 130 mph.

Comparison should stay tied to the stated tests. Table tennis specifications describe a ball falling onto a steel block, whereas the basketball requirement describes a drop from 1800 mm and a measured rebound range. Driver COR values concern a club and ball collision at stated speeds rather than a ball dropped onto a surface.

Rather than setting a universal ranking for every real-world impact, these figures show how rebound benchmarks depend on the object and test arrangement. FIBA’s standard provides basketball a return-height target for comparison.

Since 2019, my used 2014 Honda Fit, with 61,000 miles in 2019, has made me wary of declaring any single condition the whole verdict. The FIBA basketball rebound check is the useful part here: it asks for a defined result after a defined drop, which is considerably less slippery than treating air pressure as the finish line.

Air Pressure in NBA Ball Rules

NBA rules set the approved ball requirement. That range is the stated equipment requirement for a ball approved for NBA play. The rule permits the stated range rather than a single number.

Within those limits, a basketball satisfies the pressure requirement named in the NBA equipment rules. Approval under that rule also requires the ball itself to be officially approved by the NBA. The NBA labels the required item an officially approved NBA ball. Pressure is expressed in pounds in the rule.

Equipment Availability Before Pregame Warmup

Additionally, the NBA requires at least nine balls to be made available to each team for pregame warmup. Each team receives that minimum number for warmup under the rule. Availability is a separate requirement from the approved ball’s pressure range.

The home team shall provide a minimum of 12 balls for pre-game warm-up. Both provisions describe game equipment and its required availability before play. Pregame warmup is the stated occasion for that minimum availability. The requirement applies to each team, so the stated count is not a combined minimum for both teams.

What the Rule Establishes

No NBA equipment detail listed here explains how pressure changes a basketball’s bounce. Temperature, ball construction, and court-surface type are likewise not addressed as bounce-changing factors in the available specifications.

Those omissions mean the 7½ to 8½ pound rule cannot, on its own, establish a different bounce result at every point in the permitted range. Instead, it defines the pressure interval required for NBA-approved game equipment. The details given for the NBA ball identify a required range, but no stated effect within that range.

Accordingly, the rule gives players, teams, and officials a clear equipment boundary: 7½ to 8½ pounds. Its direct statement in the NBA specifications defines the approved ball’s pressure and separately requires official NBA approval. Readers can therefore distinguish an equipment rule from a bounce prediction.

NBA rules also specify that each team has at least nine balls for pregame warmup, connecting the standard to the balls available before a game. Beyond pressure and availability, these rules do not provide a measured change in rebound height, collision outcome, or performance for a basketball. No other pressure figure appears in the listed NBA ball requirement.

Why a Basketball Does Not Return to Full Height

A basketball rebounds below its drop height because its collision with the floor is not perfectly elastic. Rather than returning all of its motion to the upward rebound, a real collision converts some kinetic energy to other forms. That loss means the ball leaves contact with less kinetic energy than it had before impact, so it cannot climb back to its original release height. Such a return would require no kinetic-energy loss during the collision.

Such complete conservation is an ideal that truly elastic collisions achieve only with subatomic particles, such as electrons striking nuclei. A basketball and a court are macroscopic objects, so their impact is not that perfect case. Instead, the rebound shows the limits of a real-world collision during each impact.

Friction and sound are two routes through which a macroscopic collision can shift kinetic energy into other forms. Heat transfer caused by friction is another identified outcome in collisions that are not perfectly elastic.

Because energy has gone into those forms, less remains available for upward motion after contact ends. Accordingly, the rebound falls short of the starting height even though the ball moves upward again. Each lost portion prevents a perfectly equal return to the release point.

Momentum can still be part of the collision story, but its conservation alone does not make an impact perfectly elastic. Therefore, an upward bounce does not show that every part of the incoming kinetic energy remains in rebound motion. Instead, the lower rise is the visible result of energy that did not stay as the ball’s upward kinetic energy when it met the court surface on its downward trip.

Those values mark the two collision endpoints.

Consequently, the lower rebound is the expected signature of an imperfect macroscopic collision, not a failure to bounce.

Frequently Asked Questions

How Does a Basketball Bounce After Hitting the Floor?

A basketball bounce begins with a collision between the ball and the floor. After impact, the coefficient of restitution compares the relative velocity of separation with the relative velocity of approach. When friction is neglected and a ball is dropped from rest onto a horizontal surface, rebound height can be used to calculate that value.

What Is the Coefficient of Restitution for a Basketball?

The coefficient of restitution, or COR, measures the springiness of a collision between two surfaces. For the cited FIBA basketball rebound requirement, the implied COR ranges from 0.758 to 0.776. A COR of 1 represents a perfectly elastic collision, while 0 represents a perfectly inelastic collision with no rebound.

How High Must a Basketball Rebound in the Cited FIBA Test?

FIBA’s cited rebound test drops a basketball from 1800 mm and requires a rebound of 1035 to 1085 mm, equal to a COR of 0.758 to 0.776. That range corresponds to a coefficient of restitution from 0.758 to 0.776. The relationship between rebound height h and drop height H is e = √(h / H) when friction can be neglected.

What Air Pressure Does the NBA Require for a Basketball?

NBA rules require an officially approved basketball to have pressure between 7½ and 8½ pounds. Teams must also have at least nine balls available for pregame warmup. The supplied specifications do not explain how changes in internal air pressure affect bounce height.

Why Does a Basketball Not Bounce Back to Its Original Height?

A basketball does not return to its original height because macroscopic collisions are not perfectly elastic. Some kinetic energy is converted into other forms, including heat transfer caused by friction and sound. As a result, the collision has a COR below 1 rather than the value of 1 associated with a perfectly elastic collision.

Basketball bounce can be described with the coefficient of restitution, which compares separation and approach velocities and links rebound height with drop height when friction is neglected. The cited FIBA requirement establishes the specified COR.

References

• Coefficient of Restitution, Wikipedia
• Elastic Collisions in One Dimension, OpenStax
• Collision Lab | Conservation of Energy • Collisions • Elasticity, PhET Simulations
• Rule No. 1: Court Dimensions and Equipment, NBA
• Basketball, Wikipedia

Sources read in September 2026.