A force acting on a particle moving in the xy plane is given by

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SUMMARY

The discussion focuses on calculating the work done by a force acting on a particle moving in the xy-plane, defined by the equation \(\vec{F} = 2y\hat{\text{i}} + x^2\hat{\text{j}}\). Participants emphasize the need to analyze the force along specific paths (OAC) and clarify that the force is not constant and varies with the particle's position. Key concepts such as dot and cross products are highlighted as essential for solving the problem. The objective is to compute the work done by the force when moving the particle from point O to point C along designated paths.

PREREQUISITES
  • Understanding of vector notation and operations in physics
  • Familiarity with work-energy principles in mechanics
  • Knowledge of dot and cross products in vector calculus
  • Ability to interpret force vectors in a two-dimensional plane
NEXT STEPS
  • Study the concept of work done by a variable force in physics
  • Learn how to apply the dot product to calculate work in vector fields
  • Explore the implications of path dependence in work calculations
  • Review examples of force fields and their effects on particle motion
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Students studying physics, particularly those focusing on mechanics and vector calculus, as well as educators looking for examples of force and work calculations in two-dimensional systems.

AryRezvani
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Homework Statement



2yoe5gx.jpg


Homework Equations



W=∫ Fx dx

The Attempt at a Solution



I think you got to split this one in terms of axis.

∫(2yi + x2j) dx

Pretty lost on it.
 
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Well, they do not say in which direction the vectors i and j point, so let us assume that vector i is parallel to the x-axis and vector j is parallel to the y-axis, which is the usual convention.

To start you off,
Path OAC:
From O to A, can you find the force on the particle along this path knowing that y = 0. In what direction does the force point from the equation given for force.? Does the force do any work along this path? Note that the particle is moving along the x-axis which is what vector direction, i or j. Can you find an equation for the path of the particle in terms of vectors i oj or both?

from A to C, same questions.

You might want to review dot and cross product as that that is what this problem seems to be designed for.

PS. Your picture shows up a bit large.
 
Understood, so quick question, is the blue line the force? Then the other lines simply components of the force?

Still a little lost. We want to calculate the work required to mvoe the object to the right first. Force is constant right? So would you use fΔrCosθ?
 
AryRezvani said:
Understood, so quick question, is the blue line the force? Then the other lines simply components of the force?

Still a little lost. We want to calculate the work required to move the object to the right first. Force is constant right? So would you use fΔrCosθ?
No, the force is not along the blue line.

No, the force is not constant.

The force depends upon the location of the particle according to \displaystyle \vec{F}=2y\hat{\text{i}}+x^2\hat{\text{j}}\ .

You are to calculate the work done by that force in moving the particle from point, O, to point, C, along each of the colored paths.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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