VanCleave's Science Fun

Your Guide to Science Projects, Fun Experiments, and Science Research

ABOUT THE SOUND PICTURE

With mouth wide open, vibrating air coming up the throat from the vocal chords leaving the open mouth and spreading in all directions. Hi, I am Janice VanCleave, author of 50+ best-selling science experiment books for children ages 4 through high school. I taught science for 27 years and now am creating this science website.   My scream was not staged. The picture was to be of two adult cats, which I was holding. A microsecond before the camera snapped, the two cats dug their claws into my skin as they prepared to leap out of my arms. A picture like this is great for making inferences. Kids could make "guesses" as to why I am screaming. They would be drawing on facts from the photo, such as I look like I am in pain or maybe I am just pretending.

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Home » Floating

Floating

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Why Do Some Heavy Objects Float and Other Heavy Objects Sink?

 

New Terms

buoyancy
buoyant force
density
displacement
fluid
volume

Whether an object sinks or floats in a fluid (liquid or gas), depends on several variables:

1. The density of the object in a fluid. (Density is the ratio of the object’s mass to volume.)

2. The density of the fluid (gas or liquid) the object is floating in.

3. If the density of the object is greater than the density of the fluid, the object sinks.
If the density of the object is equal to or is less than the density of the fluid, the object floats.

Does the Bowling Ball In The Diagram Sink or Float?

The diagram shows the bowling ball on the bottom of the container of water. But, assuming it is being held in place on the bottom, will it float when released?
Think!
1. If the density of the bowling ball is greater than the density of the water it is submersed in, it will not float. If the ball’s density is equal to or less than the density of the water, the ball will float.

2. Calculate the density of the bowling ball using this formula:  density = mass ÷ volume

d = 5.5 kg  ÷  4.5 liters

   = 1.2 kg/1liter or 1.2 kg per 1 liter

3. Calculate the density of the displaced water using the same density formula: density = mass ÷ volume

d = 4.5 kg  ÷  4.5 liters

            = 1.0 kg/1liter or 1.0 kg per 1 liter

Answer:  The density of the bowling ball is greater than the density of the displaced water, thus the bowling ball will not float. The bowling ball sinks in this water.

 

Challenge: Do All Bowling Balls Sink? How Does the Weight of a Ball Affect Its Ability to Float

The density of a twelve pound bowling ball is greater than that of water, thus the ball sinks in water.

The bowling ball is completely submerged in the water, thus the ball displaces a volume of water equal to the volume of the bowling ball. The mass of the bowling ball is greater than the mass of the displaced water. Density is the ratio of mass to volume, thus the density of the displaced water is 1kg/1liter and the density of the bowling ball is 1.2 kg/1 liter. Since the density of the bowling ball is greater than the density of water, the ball sinks.

 

33101X: Sticky, Gloppy, Wacky, and Wonderful Experiments This Book Has Experiments for These Topics: Astronomy, Biology, Chemistry, Earth Science, and Physics