Rethinking Newton’s Laws: How Shape and Structure Change the Rules of Motion

For centuries, Newton’s Third Law of Motion—”for every action, there is an equal and opposite reaction”—has been a bedrock principle in physics. But what if the real world is more complicated? What if the shape, material, and structure of objects play a hidden role in how forces interact?

A groundbreaking study by Shimla-based physicist Ajay Sharma, published in Physics Education (April–June 2024), challenges the traditional understanding of Newton’s law. His research suggests that the classic version, while elegant, may not fully capture the messy, asymmetrical nature of real-world physics—where no two objects are perfectly identical.

The Missing Piece: Why Shape Matters

Newton’s law assumes that forces between two objects are always equal and opposite. But Sharma argues that this isn’t always true when objects differ in shape, composition, or surface contact. His paper, “Shape Dependent Form of Newton’s Third Law of Motion,” introduces a new factor—‘Q’—a dimensionless coefficient that adjusts the reaction force based on real-world variables.

In Sharma’s updated equation:
Reaction = –Q × Action

Here, Q accounts for:

• Shape asymmetry (e.g., a cube vs. a sphere)
• Material differences (steel vs. rubber)
• Contact surface texture (smooth vs. rough)
• Environmental conditions (like air resistance or friction)

When Q = 1, the law reverts to Newton’s original form. But in most real-world cases, Sharma suggests, Q may not be 1—meaning the reaction force isn’t always equal.

A Thought Experiment: Dropping Balls in a Vacuum

To illustrate his point, Sharma describes a simple yet revealing scenario: What happens when two objects of the same mass but different shapes (say, a sphere and a cube) are dropped in a vacuum?

Even if both have identical mass and material, their rebounding behavior differs—the sphere bounces predictably, while the cube may tumble unevenly. This inconsistency, Sharma argues, shows that Newton’s law oversimplifies real interactions.

Implications for Rockets, Robots, and Beyond

If Sharma’s theory holds, it could reshape how we model forces in:

• Space travel (adjusting rocket propulsion equations)
• Robotics (improving grip and impact resistance)
• Particle physics (refining collision models)

Classical equations, like those for elastic collisions or the Tsiolkovsky rocket equation, assume idealized conditions. Sharma’s work suggests they might need tweaking for real-world accuracy.

Not Replacing Newton—But Refining Him

Sharma isn’t dismissing Newton’s law—he’s expanding it. His proposal invites physicists worldwide to test ‘Q’ in different scenarios. If experiments confirm his model, it could bridge the gap between textbook physics and the complexities of modern engineering.

“Science evolves by questioning even the most fundamental ideas,” says Sharma. “This is not about overturning Newton—it’s about making his genius even more useful for today’s challenges.”

The physics community will need to put Sharma’s theory to the test. If validated, this could be a small step for a paper—but a giant leap for applied physics.