In this article, we dive into the cool world of physics by exploring buoyancy and weight distribution. We’ll do this through a simple experiment using two different balls: a hanging acrylic ball and a ping pong ball.
To start, we have a balance scale and two beakers filled with water. One beaker has a hanging acrylic ball, and the other has a ping pong ball attached to the bottom. Our mission is to see how the balance changes when these balls are placed in the water.
When we let go of the balance, it tips towards the beaker with the hanging acrylic ball. But why does this happen?
Both balls push aside the same amount of water, which means they both feel the same upward push, called buoyant force. Archimedes’ Principle tells us that this force is equal to the weight of the water each ball moves out of the way. But according to Newton’s Third Law, there are equal and opposite forces acting on the water in both beakers.
For the beaker with the hanging ball, the weight goes up by the amount of water pushed aside. This happens because the buoyant force now helps hold up some of the weight that was previously held by the string. So, this beaker becomes heavier.
On the other hand, for the beaker with the ping pong ball, the downward force on the water is mostly balanced by the upward pull of the string. This means the weight of this beaker only goes up by the weight of the ping pong ball itself. That’s why the beaker with the hanging ball ends up being heavier.
To learn more about these ideas, let’s try a new experiment. This time, instead of tying the ping pong ball, we’ll hold it just below the water’s surface with a finger. What do you think will happen when the scale is free to move?
We invite you to guess the outcome of this new setup. Will the balance tip towards the hanging acrylic ball (Option A), the submerged ping pong ball (Option B), or stay perfectly balanced (Option C)? Share your guesses in the comments, starting with A, B, or C, and explain why you think so.
This experiment with buoyancy and weight distribution not only shows us some basic physics principles but also gets us thinking like scientists. Stay tuned to find out the results of your predictions in the next part!
Think about objects that float and sink in water. Make a list of at least five items you believe will float and five that will sink. Then, test your predictions at home or in class using a bowl of water. Discuss why each item behaved the way it did based on the concept of buoyancy.
Using a small container, measure the volume of water displaced by different objects. Calculate the buoyant force using Archimedes’ Principle: $$F_b = rho cdot V cdot g$$, where $F_b$ is the buoyant force, $rho$ is the density of water, $V$ is the volume of displaced water, and $g$ is the acceleration due to gravity. Share your findings with the class.
In groups, discuss how weight distribution affects balance. Use a seesaw or a simple lever setup to experiment with different weight placements. Explain how Newton’s Third Law applies to your observations and how it relates to the experiment with the acrylic and ping pong balls.
Recreate the experiment with the acrylic and ping pong balls. Before conducting the experiment, write down your predictions about the outcome. After the experiment, compare the results with your predictions and discuss any differences. What did you learn about buoyancy and weight distribution?
Design your own experiment to explore buoyancy and weight distribution. Choose different objects and liquids (e.g., oil, saltwater) to see how they affect buoyancy. Present your experiment to the class, explaining your setup, hypothesis, and findings.
Buoyancy – The upward force that a fluid exerts on an object that is submerged or floating in it. – When a boat floats on water, it is because the buoyancy force is equal to the weight of the boat.
Weight – The force exerted on an object due to gravity, calculated as the mass of the object multiplied by the acceleration due to gravity ($w = mg$). – The weight of an object on Earth can be calculated by multiplying its mass by $9.8 , text{m/s}^2$.
Experiment – A scientific procedure undertaken to test a hypothesis by collecting data and making observations. – In our science class, we conducted an experiment to see how different materials affect the speed of a rolling ball.
Force – A push or pull on an object that can cause it to change its velocity, direction, or shape, measured in newtons (N). – The force required to move a box across the floor depends on the friction between the box and the floor.
Water – A transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth’s streams, lakes, and oceans. – Water is essential for life and plays a crucial role in many scientific experiments, such as studying buoyancy.
Balance – A state where opposing forces or influences are equal, or a device used to measure mass. – In the lab, we used a balance to measure the mass of different objects accurately.
Principle – A fundamental truth or proposition that serves as the foundation for a system of belief or behavior or for a chain of reasoning. – Archimedes’ principle explains why objects float or sink in a fluid based on their density compared to the fluid.
Acrylic – A synthetic material often used in science experiments for its transparency and durability. – We used an acrylic container to observe the behavior of light as it passed through different mediums.
Ping Pong – A lightweight ball used in the game of table tennis, often used in experiments to demonstrate principles of motion and energy. – In our physics class, we used a ping pong ball to demonstrate how air pressure can keep it suspended in a stream of air.
Scientist – A person who conducts scientific research to advance knowledge in an area of interest. – Marie Curie was a renowned scientist who made groundbreaking discoveries in the field of radioactivity.
