What are the forces and displacement involved in this body's movement?

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Homework Help Overview

The discussion revolves around a physics problem involving a 2.3 kg body moving along the positive x-axis under the influence of a force that varies with displacement. The force is given as Fx = -3x N, and the problem asks for the body's velocity at different positions along the x-axis.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore the implications of a non-constant force and its relationship to acceleration. There is discussion about the validity of using certain kinematic equations and the nature of the force being conservative or not. Some participants attempt integration to find displacement and velocity.

Discussion Status

The discussion is active, with participants questioning the assumptions about the force and its effects on motion. Some guidance has been offered regarding the use of force equations and the nature of acceleration, but there is no explicit consensus on the approach to solve part B of the problem.

Contextual Notes

Participants note the complexity introduced by the non-constant force and the need for calculus to address the problem effectively. There is also mention of the importance of showing work in detail for better assistance.

nabilsaleh
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Homework Statement



The only force acting on a 2.3 kg body as it moves along the positive x-axis has an x component Fx = -3x N, where x is in meters. The velocity of the body at x = 2.8 m is 11 m/s. (a) What is the velocity of the body at x = 3.6 m? (b) At what positive value of x will the body have a velocity of 3.0 m/s?



Homework Equations





The Attempt at a Solution



i got the answer for part A (10.73m/s) but I'm stuck in B! HELP!

i tried vf^2=vi^2 +2Ax for part a. But i just don't know wat to substitute in B.
 
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This is not a constant force, so the equation vf^2=vi^2 +2Ax is not valid. What motion is it when the force is proportional to the displacement and opposite to it?

ehild
 
ehild said:
What motion is it when the force is proportional to the displacement and opposite to it?

ehild

negative acceleration, right?
 
And what is the sign of the acceleration when x is negative?

ehild
 
ehild said:
And what is the sign of the acceleration when x is negative?

ehild

positive...so?
 
The acceleration is not constant. Is the force conservative?

ehild
 
ehild said:
The acceleration is not constant. Is the force conservative?

ehild

no the force is not conservative. so do we use f=ma? but in that case wat is a ?!
 
a=F/m. And how do you know that this force is not conservative?

ehild
 
ehild said:
a=F/m. And how do you know that this force is not conservative?

ehild


obviously the force changes according to displacement. but how could a=f/m benefit us? i didn't get where you're trying to get with this...
 
  • #10
Have you learned calculus? Or have you learned about simple harmonic motion?

ehild
 
  • #11
ehild said:
Have you learned calculus? Or have you learned about simple harmonic motion?

ehild

i did. but can you elaborate please. I am having a hard time following you here :S
 
  • #12
ehild said:
Have you learned calculus? Or have you learned about simple harmonic motion?

ehild

i tried integrating (w= (integral) fd )
and i got x=9.7

PLEASE CHECK MY ANSWER! this is important!
 
  • #13
nabilsaleh said:
i tried integrating (w= (integral) fd )
and i got x=9.7

PLEASE CHECK MY ANSWER! this is important!

The result is all right. But you get proper help earlier if you show your work in detail.

ehild
 

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