Resultant Force vs. Net Force: Clarifying the Difference

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The discussion clarifies that while resultant force and net force are often considered synonymous, the statement "the motion of a body is always in the direction of the resultant force" is incorrect. In scenarios such as circular motion, the velocity of the body is perpendicular to the net force, demonstrating that motion does not always align with the direction of the resultant force. Replacing "motion" with "acceleration" in the statement maintains its validity in circular motion. Participants acknowledged the distinction and the importance of understanding these concepts in physics. Overall, the conversation emphasizes the nuanced relationship between force, motion, and acceleration.
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the motion of a body is always in the direction of the resultant force. Why wouldn't this be a correct statement?

I thought all the forces on a body were added up and the resultant force was the direction in which the body moved. Am I confusing net force with resultant force? I was under the impression that they meant the same thing..
 
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I'd probably replace the word "motion" with "acceleration" in the first post.
 
Hey Russ,
Thanks for the reply. I just checked out your website, and its really cool!
 
iurod said:
the motion of a body is always in the direction of the resultant force. Why wouldn't this be a correct statement?

I thought all the forces on a body were added up and the resultant force was the direction in which the body moved. Am I confusing net force with resultant force? I was under the impression that they meant the same thing..

They are the same.
But the statement "the motion of a body is always in the direction of the resultant force" is wrong. In circular motion with constant speed, velocity is perpendicular to net force.
 
hikaru1221 said:
They are the same.
But the statement "the motion of a body is always in the direction of the resultant force" is wrong. In circular motion with constant speed, velocity is perpendicular to net force.

I didn't think of that until now. I guess circular motion totally proved this statement to be incorrect. Thanks for clarifying this for me hikaru
 
If you replace "velocity" with "acceleration" the statement still holds in the case of circular motion.

Thanks for the compliment on my website.
 
I have recently been really interested in the derivation of Hamiltons Principle. On my research I found that with the term ##m \cdot \frac{d}{dt} (\frac{dr}{dt} \cdot \delta r) = 0## (1) one may derivate ##\delta \int (T - V) dt = 0## (2). The derivation itself I understood quiet good, but what I don't understand is where the equation (1) came from, because in my research it was just given and not derived from anywhere. Does anybody know where (1) comes from or why from it the...
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