Question on Newton's first law

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Discussion Overview

The discussion revolves around Newton's First Law of Motion, specifically addressing why an object with no resultant force can still move at a constant velocity. Participants explore the relationship between motion, force, kinetic energy, and momentum.

Discussion Character

  • Conceptual clarification, Technical explanation, Debate/contested

Main Points Raised

  • Some participants assert that an object with no resultant force can maintain constant velocity, linking this to Newton's First Law of Motion.
  • There is a suggestion that kinetic energy is relevant to the discussion, but it remains unclear how it directly relates to the absence of force.
  • Another participant introduces the concept of momentum, indicating that changes in speed affect both momentum and kinetic energy, which require force.
  • One participant notes that common sense may mislead understanding, referencing Galileo's insights on friction and air resistance that complicate the perception of motion.

Areas of Agreement / Disagreement

Participants express varying views on the role of kinetic energy and momentum in relation to Newton's First Law. The discussion does not reach a consensus on how these concepts interrelate.

Contextual Notes

Some assumptions about the definitions of force, motion, and energy are not explicitly stated, which may affect the clarity of the discussion. The influence of external factors like friction and air resistance is acknowledged but not fully resolved.

Lim Y K
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An object with no resultant force can still be moving at constant velocity. Why? Is it because of its kinetic energy or has it got nothing to do with energy?
 
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Lim Y K said:
An object with no resultant force can still be moving at constant velocity. Why? Is it because of its kinetic energy or has it got nothing to do with energy?
An object which is moving which also has no net force acting on it continues to move without change in its motion. That's Newton's First Law of Motion.

If you want to make an object go slower, you must apply some force to it.
If you want to make an object go faster, you must apply some force to it.
If you want the motion of the object to stay the same, don't apply any force to it.

Newton's First Law is not concerned with how the motion of the object started initially, only what happens to the object while it is in motion (or not, as the case may be).
 
Lim Y K said:
Is it because of its kinetic energy or has it got nothing to do with energy?

In addition to SteamKing's answer: It is because of its momentum but it has also to do with energy. Changing the speed changes momentum and kinetic energy and both require a force.
 
Common sense and intuition can be deceptive. In everyday experience a constant force may seem to be needed to keep an object moving. However, Galileo discovered that friction and air resistance were obscuring underlying laws. Galileo is quoted verbatim in Newton's First Law.
 

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