The Unchanging Weight of an Object: An Explained Experiment and the Role of Gravity

If there were no forces acting upon a body it would NOT have weight! Weight IS the result of gravitational force.
- Unknown

One of the intriguing aspects of physics is the concept of weight and how it remains constant under certain conditions. This article will explore a simple experiment that many of us have encountered and understand the underlying principles of weight and gravity. We will delve into the reasons why the weight of an object does not change during specific scenarios and discuss the role of gravitational force. Additionally, we will analyze the experiment presented and its implications in the context of Newton's laws of motion.

Understanding Weight and Gravitational Force

Weight is a measure of the force exerted on an object due to gravity. It is defined as the product of the mass of the object and the gravitational acceleration at that location (w mg, where w is weight, m is mass, and g is gravitational acceleration).

Gravitational force is the attractive force between two masses. The strength of this force depends on the masses of the objects and the distance between them, as described by Newton's law of universal gravitation (F G * (m1 * m2) / r^2).

Newton's Laws of Motion and Weight

Newton's laws of motion provide a framework for understanding the behavior of objects under the influence of various forces. The first law, the law of inertia, states that an object remains at rest or in uniform motion unless acted upon by a net external force. In the context of weight, this means that if an object is not experiencing any net external force other than gravity, its weight will remain constant.

The second law, F ma, relates the force acting on an object to its mass and acceleration. If the only force acting on an object is gravity, the acceleration due to gravity is constant, and the weight of the object will not change.

The third law, action and reaction, states that for every action, there is an equal and opposite reaction. In the context of weight, this means that the gravitational pull of the Earth on an object is always matched by the equal and opposite pull of the object on the Earth. This interaction keeps the object and the Earth in motion but does not change the weight of the object.

A Simple Experiment to Illustrate the Concept

Let's revisit the simple experiment mentioned at the beginning. When you take six cans of a nutritional supplement beverage from the deli and freeze them, the weight of these cans does not change. This might seem counterintuitive, especially if the cans turn from a liquid to a solid or change in volume. However, the weight remains the same because no other external force is acting on the cans other than gravity.

Here's a step-by-step breakdown of the experiment:

Visit the deli at the supermarket and purchase a six-pack of a nutritional supplement beverage.

Ask the deli employee to weigh the six-pack on the calibrated scale. Record this weight.

Place the six-pack in the freezer at the deli.

Wait for 48 hours for the cans to freeze.

Return to the deli and weigh the frozen six-pack again. Record this weight.

Compare the two recorded weights. They should be identical.

Explanation: The temperature change during the freezing process does not affect the weight of the cans because the mass (content of the cans) does not change. The weight of an object is a measure of the gravitational force acting on that object. Since the only force acting on the cans is gravity, and there are no significant other forces (such as air resistance, etc.), the weight remains constant.

Implications and Applications

Understanding the relationship between weight and gravitational force has practical applications in various fields, including:

Space Exploration: In space, objects experience microgravity, where the gravitational force is significantly reduced. This is why astronauts can float and interact with objects in a way that is different from how they would on Earth.

Astronomy: Observing the effects of gravitational force on celestial bodies can help scientists understand the structure and dynamics of galaxies, stars, and planets.

Meteorology: Studying the effects of gravitational force on atmospheric conditions can help predict weather patterns and climate changes.

Conclusion

In conclusion, the weight of an object remains constant when no external forces, other than gravity, are acting on it. This concept is rooted in Newton's laws of motion and has profound implications across various scientific disciplines. From understanding the behavior of objects in everyday scenarios to advancing our knowledge of space and beyond, the principles of weight and gravitational force continue to be crucial to our understanding of the universe.