Newton's First Law of Motion is Wrong (Proven Wrong in This Thread)

Click For Summary
SUMMARY

This discussion critically examines Newton's First Law of Motion, asserting that it is incorrect based on an inelastic collision experiment involving two balls. The balls, moving at 5 m/s towards each other on a frictionless plane, come to rest upon collision, contradicting the law's claim that an object in motion will remain so unless acted upon by an external force. Participants emphasize that during the collision, forces are indeed exerted between the balls, leading to a change in velocity and acceleration, thus validating Newton's Second Law, which states that Force equals Mass times Acceleration (F = ma).

PREREQUISITES
  • Understanding of Newton's First Law of Motion
  • Familiarity with Newton's Second Law of Motion (F = ma)
  • Basic knowledge of inelastic collisions
  • Concept of acceleration and its calculation
NEXT STEPS
  • Research the principles of inelastic collisions in physics
  • Study the implications of Newton's Laws in real-world scenarios
  • Explore advanced topics in classical mechanics, including momentum conservation
  • Learn about experimental methods to demonstrate Newton's Laws
USEFUL FOR

Physics students, educators, and anyone interested in the foundational principles of motion and mechanics will benefit from this discussion.

NewtonWasWrong
Messages
2
Reaction score
0
Please note this is a very serious thread.

Please note Newton's First Law:

First law: When viewed in an inertial reference frame, an object either remains at rest or moves at a constant velocity, unless acted upon by an external force.


Here is an experiment to prove this First Law wrong.
Consider two balls rolling at a constant velocity directly toward each other on a frictionless plane. Ball A is heading due east at 5 m/s and Ball B is heading due west at 5 m/s. The balls engage in an inelastic collision. The balls will both come to rest. This can be proven experimentally.

Please note that Newton's Second Law describes Force = Mass * Acceleration. Neither ball has an acceleration, meaning that neither ball has any force associated with it. So despite not being acted upon by any FORCE, during the collision, the balls change velocity from 5 meters/second to zero. This simple experiment clearly shows that an object will not necessarily stay in motion at a constant velocity despite not being acted upon by an external force.
 
Science news on Phys.org
NewtonWasWrong said:
Please note that Newton's Second Law describes Force = Mass * Acceleration. Neither ball has an acceleration, meaning that neither ball has any force associated with it. So despite not being acted upon by any FORCE, during the collision, the balls change velocity from 5 meters/second to zero. This simple experiment clearly shows that an object will not necessarily stay in motion at a constant velocity despite not being acted upon by an external force.
This is silly. When the balls collide they exert forces on each other!
 
  • Like
Likes   Reactions: russ_watters
Doc Al said:
This is silly. When the balls collide they exert forces on each other!
Please note Newton's Second Law of Motion:

Second law: The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object; thus, F = ma.

Please note that the acceleration of both balls are equal to 0. Please note that mass*0=0. Consequently, neither ball produces a force (or rather, produces a force equal to 0).
 
NewtonWasWrong said:
Please note that the acceleration of both balls are equal to 0.
Only before they collide! Once they collide, they certainly have a non-zero acceleration. You indicated such yourself!
 
NewtonWasWrong said:
Please note Newton's Second Law of Motion:

Second law: The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object; thus, F = ma.

Please note that the acceleration of both balls are equal to 0. Please note that mass*0=0. Consequently, neither ball produces a force (or rather, produces a force equal to 0).

In the collision, both balls change their speed from five meters/second to zero meters per second. That's an acceleration, and you can even calculate its average value throughout the collision: If the time between when the balls first touch andwhen they stop moving is ##\Delta{t}## seconds, the average magnitude of the acceleration will be ##\frac{\Delta{v}}{\Delta{t}} = \frac{5}{\Delta{t}} m/sec^2##.

Non-zero ##a##, non-zero ##m##, got to be a non-zero ##F##.
 
  • Like
Likes   Reactions: 1 person
NewtonWasWrong said:
Please note this is a very serious thread.
Next time, before posting an obviously wrong and completely ignorant challenge to an established theory it might be good to exercise a little humility and actually learn enough of the theory to be able to use it correctly.

You completely failed to recognize the obvious forces acting on the objects, and therefore completely failed to correctly apply the theory. Furthermore, you arrogantly assumed that you were the only person in the last 300 years smart enough to have correctly analyzed an inelastic collision using the theory.
 
  • Like
Likes   Reactions: russ_watters, Vanadium 50, vanhees71 and 3 others

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 41 ·
2
Replies
41
Views
2K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 14 ·
Replies
14
Views
8K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 28 ·
Replies
28
Views
4K
  • · Replies 11 ·
Replies
11
Views
3K