Net Force & Motion: A 9th Grader's Guide

In summary, a body will have a constant velocity if the net force acting on it is zero. This means that if it was initially at rest, it will remain at rest, and if it was moving with a certain velocity, it will continue moving with the same velocity. However, it may not always be at rest, as it can also be moving at a constant velocity. The definition of force is something that changes the velocity of an object, causing it to accelerate. If the net force is zero, the body may either be moving at a constant velocity or be at rest, as there is no acceleration. This is in accordance with Newton's first law, which states that a force is only needed to accelerate a body. An everyday example
  • #1
proyasha
9
0

Homework Statement



will a body necessarily remain at rest if the net force acting on it is zero?give a reason for ur answer...and I've just passed my ninth grade so if u cud please it to me explain at that level...:smile:



Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
  • #2
proyasha said:
will a body necessarily remain at rest if the net force acting on it is zero?

It will have a constant velocity. If it was initially at rest, it will be at rest. If it was moving with a certain velocity, it will continue moving with the same velocity.
 
  • #3
it would not always mean it will be at rest because it can also be moving at constant velocity since the definition of force is something that would change the velocity of an object therefore making it accelerate but if the net force is zero then it could either be moving at constant velocity or be at rest since there is no acceleration.
 
  • #4
Google_Spider said:
It will have a constant velocity. If it was initially at rest, it will be at rest. If it was moving with a certain velocity, it will continue moving with the same velocity.

princesspriya said:
it would not always mean it will be at rest because it can also be moving at constant velocity since the definition of force is something that would change the velocity of an object therefore making it accelerate but if the net force is zero then it could either be moving at constant velocity or be at rest since there is no acceleration.

And Newton's first law says this directly.
 
  • #5
Your question is just the question Aristotle asked in a different way.
He said that a force is necessary to keep a body in motion.
As the honorary members above already have told you that Newton's first law says this directly that a force is needed only to accelerate a body.

Of course Aristotle's assumption was wrong.
 
  • #6
physixguru said:
Of course Aristotle's assumption was wrong.

If memory serves me correctly, the end result of Aristotle's assumption was that F=mv while Newton said that F=ma
 
  • #7
I am talking about "Aristotle's Fallacy".
 
  • #8
can you give an everyday example to support the answer?
 
  • #9
proyasha said:
can you give an everyday example to support the answer?

Answer me this first.

If Newton was correct then why does the Earth revolve around the sun? The gravitational pull of the sun makes the Earth go about it.But this contradicts Newton's law that a force is not necessary to keep a body in motion? :p

Answer me the logic behind this phenomenon.I am not making a statement.I am asking a question.
 
  • #10
well,i think that the sun's gravitational force provides the centripetal force which makes the Earth go about it.had the gravitational pull not been there then the Earth would have traveled in a linear path...is that what u want me to answer?..that why does the Earth REVOLVE around the sun?...and I've got another question: is there any difference between a body which has acceleration and abody which is in motion?:confused:
 
  • #11
A body in motion may not have acceleration.It may have constant velocity.
A body in acceleration may have positive or negative acceleration.This will affect its speed.
Also a body having acceleration may possesses zero velocity.
 
  • #12
okay...what about my answer?is it "logical" enough??
 
  • #13
There is a theory that the planets don't actually "revolve" around the sun.

According to Einstein's theory, any mass warps space around it. (Imagine a heavy lead ball placed on a bed. The surface of the bed will bend/sag below the ball and the ball will sink into a depression. The ball represents the mass, and the bed represents space.)

Therefore, the planets, relative to themselves, are actually following a straight line. But since the sun (a mass) warps space around it, the planets appear to follow a circular path around the sun.

But to answer your question at our level, any two masses exert gravitation forces on each other (Newton's Law of Universal Gravitation). Therefore the force of attraction between the sun and the Earth is large enough to make the Earth veer off from the straight line path that it would have otherwise followed by Newton's First Law and to make it follow an ellipsis.
 
  • #14
ok... i just read that on some site the other day..(no complains there)...but what abt my example...i'm not crystal clear abt it
 
  • #15
physixguru said:
Answer me this first.

If Newton was correct then why does the Earth revolve around the sun? The gravitational pull of the sun makes the Earth go about it.But this contradicts Newton's law that a force is not necessary to keep a body in motion? :p

Answer me the logic behind this phenomenon.I am not making a statement.I am asking a question.

I think you forgot to consider circular motion as an accelerating motion. Newton's right.
Aristotle forgot to consider frictional force.
That's where he went wrong.
 

1. What is net force?

Net force is the overall force acting on an object, taking into account both magnitude and direction. It is the sum of all the individual forces acting on the object.

2. How is net force calculated?

Net force is calculated by adding together all the forces acting on an object in a given direction. If the forces are acting in opposite directions, the net force is found by subtracting the smaller force from the larger one.

3. What is the relationship between net force and motion?

Net force is directly related to the motion of an object. If the net force acting on an object is zero, the object will remain at rest or continue moving at a constant velocity. However, if the net force is not zero, the object will accelerate in the direction of the net force.

4. How does mass affect net force and motion?

The greater the mass of an object, the more force is needed to accelerate it. This means that a larger net force is required to cause the same amount of acceleration in an object with a greater mass compared to an object with a smaller mass.

5. What are some real-life examples of net force and motion?

Some examples of net force and motion in everyday life include a ball rolling down a hill due to the force of gravity, a car accelerating on a flat road due to the engine's force, and a book staying in place on a table due to the force of friction.

Similar threads

  • Introductory Physics Homework Help
Replies
30
Views
2K
  • Introductory Physics Homework Help
Replies
10
Views
239
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
8
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
4K
  • Introductory Physics Homework Help
Replies
18
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
271
Back
Top