How high will a basketball bounce

Surface Science: Where Does a Basketball Bounce Best?

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Key concepts
Energy
Gravity
Physics
Sports
 
Introduction
Playing basketball can be hard work. Players not only have to run around the court, but just dribbling the basketball takes some serious effort, too. Have you ever wondered why that is? The challenge has to do with how the basketball bounces. When the ball hits the court, its bounce actually loses momentum by transferring some of its energy—into a different form. This means that to keep the ball bouncing to the same height, players must continually put energy into the ball with each bounce. In this activity you will explore how high a basketball bounces on different surfaces compared with the height from which it was dropped. Which surface lets the basketball bounce the highest? Grab a basketball and try this activity to find out!
 
Background
Playing a game of basketball can be great exercise, and one part of that workout comes from just dribbling the ball. Why is this? When a basketball hits the ground (and as it flies through the air), it actually transforms some of its energy to another form. If players do not put enough energy back into the ball, they will not be able to dribble it effectively.
 
When a basketball bounces, it has two different types of energy: kinetic and potential. Kinetic is the energy an object has due to its motion. Potential energy is that which is stored in an object—its potential for motion—such as due to its height above the ground. For example, when you hold a basketball at waist level, it has some potential energy. If you drop the basketball, the force of gravity pulls it down, and as the ball falls its potential energy is converted to kinetic energy. When a basketball hits a court floor, a part of the kinetic energy gets converted into sound or heat, some of it briefly changes the ball’s shape (flattening it slightly) and a portion is absorbed by the floor surface.
 
Materials

• At least two different surfaces to bounce a basketball on, with at least one hard surface and one soft surface (For example, you could use carpet, concrete, grass, linoleum and a basketball court. The surface needs to be flat and next to a wall or other large perpendicular surface.)
• Tape measure or yardstick
• Painter's tape or masking tape
• Basketball
• A helper
• Video camera and access to a computer or a large screen on which to watch your recorded video (optional)

 
Preparation

• Prepare the walls or other vertical surfaces next to the floor types you want to test so that you can estimate the height of the basketball's bounce. To do this use a tape measure or yardstick along with the painter's or masking tape to mark every eight inches, starting from where the wall meets the floor and going up to 40 inches high on the wall. You should end up with five tape marks on each wall.
• If you are using a video camera, ask your volunteer to set it up so that all of the marked wall measurements as well as the floor are in view. When you're ready to test the basketball on a surface, ask your volunteer to start the video camera.
• If you are not using a video camera, ask your volunteer to get ready to watch when you drop the basketball to see roughly how high it bounces after it first hits the ground.

 
Procedure

• Hold the basketball so that the bottom of it is lined up with the top edge of the highest tape mark you made.
• Drop the ball. (Do not push it down.)
• Let the basketball bounce back up and then hit the ground a second time before you catch it in your hands (then stop recording if you were doing so). How high does your volunteer say the basketball bounced after hitting the ground the first time?
• Repeat this, dropping the basketball on the same surface a few more times to give you a good idea of just how high it bounces when being dropped from a certain height.
• Repeat this entire process with the other surface(s) you want to test. How high does the basketball bounce off another surface compared with the first one you tested? Why do you think this is?
• Tip: If you are testing a surface that is at a very different temperature (such as concrete outside on a cold day), you will want to do your testing quickly so that the ball does not change temperature too much. A change in the ball's temperature can also affect how it bounces.
• If you videotaped the basketball bounces, watch your videos to try to more closely estimate the basketball's bounce height on the different surfaces.
• Extra: Try to quantify your results from this activity. To do this, you'll want to videotape your bounce trials and closely watch the videos on a large screen to determine the exact height of the basketball before it was dropped and the highest point of its first bounce. You could even graph your results. Exactly how high does the basketball bounce on each of the different surfaces?
• Extra: A basketball loses kinetic energy by transferring it into other forms when the ball bounces. But just how many bounces can a basketball make before losing all of its kinetic energy and stopping bouncing? And how does this change if you alter some factors, such as the type of surface the basketball bounces on or the drop height? Design an experiment to investigate how many bounces a basketball can make and how various factors affect that number, and then try it out!

 
Observations and results
Did the basketball bounce much higher on the harder surface compared with the softer one?
 
One factor that can affect the basketball's collision with the ground is the type of surface the ball collides with. When a basketball bounces off of a surface, some of its energy is absorbed by that surface. Some surfaces absorb more energy than others do. (How much energy gets absorbed determines how much energy a player has to put back into the ball to keep it bouncing.) A hard surface, such as concrete, absorbs less energy compared with a soft surface, such as a carpeted floor. The more energy absorbed by the surface, the less that remains in the ball for it to bounce. This is why you should have seen that when you bounced the basketball on a relatively hard surface it bounced higher (it lost less energy) compared with when it was bounced on a softer surface (where it lost more energy). For example, depending on the type of basketball and surface, you may have seen the ball bounce about 15 inches high on carpet and about 25 inches high on concrete.
 
More to explore
Physics of Dribbling a Basketball, from Physics
Elastic and Inelastic Collisions, from HyperPhysics, Georgia State University
Fun, Science Activities for You and Your Family, from Science Buddies
Bouncing Basketballs: How Much Energy Does Dribbling Take?, from Science Buddies

This activity brought to you in partnership with Science Buddies

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Most recent answer: 10/22/2007

Q:

how high can a basketball bounce
- miguel (age 19)
maryland

A:

How high a basketball will bounce on how hard you throw it at the ground. If you drop a basketball without throwing it at the ground, it will bounce back up to a fraction of its original height that is not too far from 1.0 (0.75 is kind of typical for a well-inflated new basketball). So if you drop a basketball from height of 20 feet, you might expect it to go back up 15 feet or so. It will continue to bounce, losing about a quarter of its height on each bounce.

If you threw the ball at the ground so that it hits the ground as fast as it would had it been dropped from 20 feet, it will bounce back to about 15 feet.

Now comes the hard part -- at what point will all this break down and the basketball will not go any higher? This happens when some of the energy of motion of the basketball is no longer available for the bounce but goes into damaging the ball and/or the floor surface. For very high bounces, air resistance also plays a role, but while it does not limit the total height, it does reduce the bounce height. (there is a limit from air resistance at which the ball goes fast enough to heat up, but I suspect the first effect of the ball being damaged during the bounce will happen at lower speeds than the air resistance problem).

During a bounce, the ball squishes against the floor and the air inside pressurizes. When the air depressurizes and the ball unsquishes, the ball springs up. The ball may squish so much that the rubber bladder inside develops a tear. This is hard to do because basketballs are reinforced with cloth and leather and/or rubber on the outside so they do not tear. My guess is that if you shoot a basketball out of a cannon at the ground at a suffiently high speed, the ball will tear apart and stay on the ground. At what speed this happens depends quite a lot on how the ball is made (and how old or worn it is, how well inflated it is, etc.). My guess (and this is only a guess! I could be very wrong on this!) is that you can get at least a few hundred feet in a single bounce without destroying the ball, but it will be very very hard to do this, not to mention dangerous! You don’t want to get hit by a basketball going that fast. And getting equipment to throw the basketball that fast may be hard to make and dangerous to operate. Dropping a basketball from a skyscraper could be an interesting experiment but that experiment is not safe for people standing below, and is certainly illegal.

Tom

(published on 10/22/2007)

Follow-up on this answer

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Still Curious?

Expore Q&As in related categories

• Bouncing, Bumping & Crashing

1.

Suppose we drop two balls from a height of about a meter, with a baseball at the top and a basketball at the bottom (Figure 1.16a). Although when dropped individually from this height, none of the balls will bounce off the floor to a noticeable height, when a pair of balls falls, an unexpected result is obtained. A basketball remains motionless on the floor, while a baseball bounces strongly, sometimes even towards the ceiling (Fig. 1.16b). The height to which a baseball bounces is always greater than the sum of the heights to which a baseball and a basketball would bounce separately. (Be careful. If the ball is hit off-center, the baseball can fly off to the side, and at this speed it can hit hard.) If you repeat the experiment, but put another small elastic ball on top of the baseball, it will fly up like rocket and can bounce even higher than a baseball, although it will receive less energy.

Fig. 1.16 / Task 1. 43. a) Before and b) after a basketball and a baseball are thrown together on a hard floor. c) Before and d) after the collision of very large and very small balls. e) Before and f) after the collision from the point of view of the big ball.

In theory, if the balls are properly matched, the top ball of a pair of thrown balls can bounce to a height 9 times greater than the height from which they were dropped. With three balls, again properly matched and, of course, under ideal conditions, the top ball can bounce to a height of 49times the height from which they were dropped. You can experiment with many different balls, such as ping pong balls, bouncy balls (super bouncy balls), or tennis balls. How do you need to pick up balls in a group so that the top ball bounces to a greater height, and why does it bounce so high?

ANSWER • When a group of two balls falls, the bottom ball bounces off the floor but collides with the top one, which is still falling. On impact, energy is transferred from the bottom ball to the top ball, and it acquires an upward velocity. If you want to transfer maximum energy to the top ball, you need the bottom ball to stop. If the balls are bouncy, the most energy is transferred when the bottom ball has three to four times the mass of the top ball. About the same ratio for a basketball and a baseball.

If the goal is to make the top ball bounce as high as possible, it should be chosen as light as possible compared to the bottom one. The height to which the top ball bounces is proportional to the square of the speed it received upon impact. If the mass of the top ball is much less than the mass of the bottom one, the top ball will gain 6 more speed and will be able to jump to a height 9 times greater than the height from which it fell.

To understand the result, consider the speed of the balls just before the collision. The top ball is falling at a speed of V , while the lower one flies up at the same speed V (Fig. 1.16c). If the impact is absolutely elastic, the upper ball will acquire a speed of 3 V (Fig. 1.16 d). This may seem wrong, but imagine for a moment that you are the first ball, and look at the situation from his point of view: you will see that the top ball is approaching you at a speed of 2 V (Fig. 1.16e), elastically reflected from you and flies away at a speed of 2 V (Fig. 1.16e). Now come back to your own point of view. The top ball flies away from the bottom one with a relative speed of 2 V . What does the bottom ball do? Since the mass of the top ball is small, the impact will not significantly change the speed of the heavy bottom ball, and it will still be approximately V , so the speed of the top ball will be V +2 V =3 V .

If we consider the fall of a group of balls, you need to arrange them so that their masses decrease from bottom to top. When the bottom ball bounces off the floor, it transfers some of the energy to the second ball. As soon as the second ball flies up, it will hit the third ball flying down and transfer some of its energy to it. Now the third ball will fly up, hit the fourth ball and so on. If you make the chain of balls big enough, you could theoretically launch the top ball into space orbit.

This text is an introductory fragment.

How to choose a basketball?

Basketball is a fast and dynamic sport. To enjoy the gameplay, you need to buy high-quality inventory. Basketball equipment is presented in a wide range. Many well-known brands are engaged in the manufacture of balls for this sport. Which option to choose? Consider the main criteria.

Types of basketballs

One of the most important selection criteria is the purpose of the ball. With this, you need to start looking for a suitable projectile, we will start with this, in total there are three types:

• for the hall;
• for the street;
• universal.

The Indoor Basketball has excellent grip on parquet. Made from nat. leather or synthetics. Professional athletes choose models with a composite coating. Microfiber provides a comfortable grip. The material muffles impacts during the dribble. It is forbidden to play on asphalt sites, as in such conditions the projectile will very quickly lose all its qualities.

For the open field (outdoor) use shells made of synthetic raw materials. This composition makes them extremely resistant to wear. Additional surface treatment enhances grip. The ball is easy to control.

Universal projectiles are made of rubber. It is resistant to wear, behaves normally on parquet and can serve for quite a long time on open street areas. Some are covered with synthetic or composite materials. Manufacturers produce goods for sites with a smooth, wooden, rubber coating.

How to decide on the material

To understand how to choose a basketball, take into account the raw materials used in production. Durable versatile basketballs are made from artificial materials. Many professional indoor balls are made from composite leather.

Genuine leather is considered the best material for the hall. The leather ball is an essential element of any professional basketball tournament. If you see the marking “Supreme Leather” on such a ball, then the manufacturer used premium leather.

Quality check

The first evaluation method is rebound. A correctly inflated ball will bounce to a height of approximately 130 centimeters. There is an alternative way. Raise the professional ball to head level, and then release it. He should bounce to the waist. Look at the quality of the nipple.

Do not sit on it or kick it to keep its original shape. Careful use preserves the correct rebound during the dribble. Elasticity is another indicator of quality. The ball must not become soft after a short play. Pump up periodically, but use only a special nozzle, and not a football needle.

Size

What size basketball should I buy? It all depends on the specifics of use. Marking No. 7 - the largest ball is intended for competitions of men's teams. The table shows absolutely all existing sizes:

Size