# Do Tennis Balls Float In Water? Let Us Know Some Facts About It

Nov 02, 2023 By Anusuya Mukherjee
Originally Published on Dec 23, 2021

Objects float due to the difference in densities, and anything that is light will be pushed upwards by the force of water.

Tennis ball weighs much lighter and, therefore, cannot sink. The buoyant force makes them float at the top.

It is quite puzzling when we see a tennis ball floating while rocks sink deep down in the water. The main concept behind floating is the density of the objects, and depending on this, water pressure acts upon the objects.

While this may seem a bit perplexing for novice readers, the concept is pretty easy to grasp when we compare this force with the gravitational force.

Just like the Earth's gravitational force pulls down the objects to the ground, the force exerted by the water pushes the objects with lighter densities on the surface. In simple words, both these forces work in opposite directions.

But the question that pops up in our mind is that how exactly do we make a ball float on the water surface with a huge gravitational force acting on it? This can be understood by the concept of buoyancy.

Buoyancy can be easily defined as the upward force of water that is exerted on the submerged lighter objects. To get a wider comprehension, let's dig into the Archimedes' Principle in the following sections.

Are you enjoying the read on tennis balls floating on water? Then don't forget to check out why do things float and how to float in the water here on Kidadl.

### Nature Of Tennis Ball

Tennis balls are light and filled with air. Because of this, the tennis balls float on the water surface. Most tennis balls weigh somewhere between 56.0-59.4 g (1.98 and 2.10 oz).

The hollow ping pong ball does not sink because of the surface tension. Normal tennis balls have a thin layer of rubber with air inside.

The plastic outer shell further makes it light, with an average density of 0.388 gm per cubic cm. This low density creates a positive buoyancy, and therefore, the tennis ball floats. However, in the case of a metal fork or a golf ball, negative buoyancy will be created, which will make these sink in water.

The more density, the more chances to sink will arise. The displaced fluid is equivalent to that of the weight of the tennis ball filled with air.

### What is the size of a tennis ball?

The size of a regular tennis ball is about 2.57-2.70 in (6.5-6.8 cm) in diameter. This size is extremely crucial for the people who play tennis. A tennis ball's shell is generally made of plastic which helps it to float in water.

Many people practice with balls called pressureless tennis balls that retain their bounce and make the practice quite lively with the partners. They are immensely popular among the players who practice regularly.

This pressureless tennis ball is not air-filled, and therefore they create a positive buoyant force, which will cause them to sink. You should avoid playing with the pressureless balls in any kind of fun water activity. You may end up losing your tennis ball for good.

In these playful scenarios and also in tennis competitions, the hollow balls with air inside and which are less dense than water, are used. Its own weight will be equal to the water displaced, which will eventually make the tennis ball float.

Pressureless tennis balls have more density than the smaller space in water it displaces.

Metal fork, a golf ball, and other objects with no air interior will sink because of the surface tension acting on these and the gravity pulling these downwards. The ability to sink or float purely depends on the density.

### Factors Due To Which Tennis Ball Floats

Mainly two factors act upon the floating mechanism of the hollow tennis ball and determine whether it will sink or float. One is the density of the tennis ball, and another is the upward force of water acting on the ball. Let's dive into these two factors in greater detail.

Anything that has mass and occupies space is termed as matter. This matter is composed of molecules whose packaging is different in the three states of matter.

Solid, liquid, and gas are these three states of matter. Of course, there are other states of matter present as well, for example, the colloids, but these three form the basis of all existing materials in the universe.

As mentioned earlier, the packaging of molecules in matter determines their characteristics. Solids get their rigidity and structure from the tightly packed molecules in them, which includes negligible intermolecular space and, thus, a very high intermolecular force of attraction.

When it comes to liquid, the molecules are loosely packed, and the intermolecular force of attraction is lower than that of the molecules in solids. This provides liquids the quality to flow and take the shape of any vessel in which they are poured.

When an object is actually dropped in the water, it displaces some amount of water that is equal to that of its weight. Two forces act upon the object, which are the downward acting force or the gravitational force, and the force acting upwards, which is the buoyant force.

If the amount of water displaced is equal in weight to that of the object, then the magnitude of the buoyant force will be equal to that of the gravity. This will compel the object to float.

However, if the weight of the object is more, the force of gravity will overpower the buoyant force, and hence, the object will sink. This ability to sink or float depends upon the compaction or the packaging of the molecules in an object, which is also referred to as density. Density is the ratio of mass to volume.

Depending on the density, we can determine whether the tennis ball floats or sinks. This is where the physical law of buoyancy or Archimedes' Principle comes into play.

The Greek mathematician, Archimedes, stated that a body that is partially or completely submerged in a fluid (fluid can be both a liquid or a gas due to the lesser intermolecular force of attraction in them) at rest is acted upon by a buoyant force or an upward force.

The magnitude of this force will be equal to the volume of the water that is displaced by the object.

Following this law, he put forth a mathematic expression that will help to determine the magnitude of this buoyant force acting on the hollow tennis ball, a ping pong ball, or any other floating object. This value can be found out from the product of the fluid volume, fluid density, and acceleration due to gravity.

### What other kinds of balls float?

Apart from tennis balls, several other objects which are less dense than water are able to float. In fact, any bowling ball or a tennis ball that weighs less than 12 lb (5.4 kg) will float.

The ping pong ball can float because it is hollow and filled with air. As a result, a positive buoyant force is not created, which will not make it sink.

Plastic balls, just like a ping pong ball, cannot float because they are very light and less dense than water. Many other companies manufacture lighter balls with air inside so that they do not sink easily.

Foil balls are also hollow and filled with air. Just like the tennis balls, which are also filled with air, the foil boat has less density. Balls with molecules packed in a tight clump sink faster.

The ball, which possesses more density, is the golf ball, which has more weight than what the tennis ball weighs. Positive buoyant forces are created that do not allow them to sink. It is easier to float in saltwater because of the more mass added to the water by the dissolved salt. Objects don't sink easily in saltwater.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for do tennis balls float? let us know some facts then why not take a look at how do ships float, or does all wood float?

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