Newton's First Law and objects in motion

In summary, Newton's first law of motion states that an object in motion will remain in motion at a constant velocity in a straight line unless acted upon by an external net force. This means that in the absence of forces, an object will maintain its state of motion. One example of taking advantage of this law is when driving a car downhill, where the force of gravity can maintain the car's speed without needing to apply extra pressure on the gas pedal. However, it is important to note that the net force can be zero even if there are multiple forces acting on an object, as seen in the case of an object at rest on the Earth's surface.
  • #1
Eddard
4
0
Im wondering what situations involving objects in motion , you could take advantage of Newton's first law of motion?

I have one situtaion but I am not sure of another one that could be considered taking advantage of Newton's law...
 
Physics news on Phys.org
  • #2
Eddard said:
Im wondering what situations involving objects in motion , you could take advantage of Newton's first law of motion?

I have one situtaion but I am not sure of another one that could be considered taking advantage of Newton's law...

What does Newton's 1st Law say about objects in motion? What situation did you come up with?
 
  • #3
Well off the top of my head Newton's first law of motion is
" An Object in a constant state of motion, will remain in a constant state of motion unless acted upon by an external net force"

I can easily think of example just not one that would be considered taking advantage of it...my example was cutting a log with an axe. You first hit the log lightly so it is stuck on the blade of the axe then you swing it down and when you hit a hard surface (A stump) the wood stops but the axe keeps moving through the log cutting it in half...
 
  • #4
Eddard said:
Well off the top of my head Newton's first law of motion is
" An Object in a constant state of motion, will remain in a constant state of motion, at uniform speed in a straight line, unless acted upon by an external net force"

I can easily think of example just not one that would be considered taking advantage of it...my example was cutting a log with an axe. You first hit the log lightly so it is stuck on the blade of the axe then you swing it down and when you hit a hard surface (A stump) the wood stops but the axe keeps moving through the log cutting it in half...
You're taking advantage of his 2nd law in your example, not his first. You are overcomplicating the 1st law, which you stated pretty well, which I have modified slightly in red above. Supposing a car is traveling on a level road at a steady speed of 60mph. It will forever stay at that speed in a straight line unless an unbalanced force acts on it. So when its moving steadily at a constant speed of 60mph, there must be no net force acting on it, that is, with your foot on the pedal, the driving force between the tires and the road is exactly counterbalanced by friction and air drag resistance forces. Now suppose you start up a hill without applying any more pressure to the pedal. Now there is an unbalanced force acting...gravity.. which will slow you down unless you give the car more gas by depressing the pedal further. If you do this, the car will then increase its speed again and will remain at constant speed as long as the now stronger driving force is exactly counterbalnced by the friction, air drag, and gravity forces. Now, supposing the car starts going downhill. Here's where you take advantage of Newton 1. Because gravity is acting downhill in your favor, the unbalanced gravity force will increase your speed, so now you can take your foot off the pedal and save on fuel by letting the gravity force, exactly counteracted by friction and air drag, keep you moving at constant speed, and further, you won't get a ticket for speeding!
 
  • #5
Newton's First law implicitly defines what a force is by describing what happens in the absence of forces.

In the absence of forces and when viewed from an inertial reference frame an object at rest will remain at rest and an object in motion will maintain its motion at a constant velocity (constant speed along a straight line).

Also, the first law implies the concept of inertial reference frames:

If an object does not interact with any other objects, it is possible to identify a reference frame in which the object has zero acceleration (thus a constant velocity which may or may not be zero).

Newton's second law tells us what happens when the net force is zero:

When viewed from an inertial reference frame, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Examining the first and second laws closely, we see there is a slight difference. Although it is correct to say that in the absence of forces an object has a net force of zero, the converse is not true. It is highly possible for an object to have several forces acting on it and the net force be zero. Case in point: an object at rest on the Earth's surface. Gravity and the normal force are acting on the object, but the net force is zero.
 

Related to Newton's First Law and objects in motion

What is Newton's First Law?

Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest and an object in motion will remain in motion with a constant velocity unless acted upon by an external force.

What is the significance of Newton's First Law?

This law explains the concept of inertia, which is the tendency of an object to resist changes in its state of motion. It also serves as the basis for understanding the behavior of objects in motion.

How does Newton's First Law apply to everyday life?

Newton's First Law can be observed in many everyday situations. For example, when a car suddenly stops, objects inside the car continue to move forward due to their inertia. This is also why it is important to wear seatbelts while driving.

Can Newton's First Law be violated?

No, Newton's First Law is a fundamental law of physics and cannot be violated. However, it may seem like the law is being violated if an external force is not evident or if the motion is not observed carefully.

How does Newton's First Law relate to other laws of motion?

Newton's First Law is often referred to as the "law of inertia" and serves as the basis for understanding the other two laws of motion. The Second Law describes how acceleration is influenced by force, while the Third Law explains the relationship between action and reaction.

Similar threads

  • Introductory Physics Homework Help
Replies
5
Views
623
  • Introductory Physics Homework Help
Replies
9
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
17
Views
673
  • Introductory Physics Homework Help
Replies
12
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
2K
  • Introductory Physics Homework Help
Replies
16
Views
628
  • Introductory Physics Homework Help
2
Replies
42
Views
3K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
711
Back
Top