Is Work Always Positive in Linear and Rotational Cases?

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SUMMARY

The discussion centers on the concept of work in both linear and rotational cases, specifically addressing the equations for calculating work. For linear work, the formula is Work = Fs, where F is constant force and s is displacement, with work being negative if displacement is in the opposite direction. In rotational work, the equation is Work = τφ, where τ is torque and φ is the resultant angle. The participants confirm that if the force aligns with the direction of displacement, work is positive; otherwise, it is negative.

PREREQUISITES
  • Understanding of linear work calculations using Work = Fs
  • Familiarity with rotational dynamics and the equation Work = τφ
  • Knowledge of torque and its role in rotational work
  • Basic grasp of angular displacement and its measurement in radians
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  • Research the implications of negative work in linear mechanics
  • Explore advanced concepts in rotational dynamics, focusing on torque
  • Study the relationship between force and displacement in both linear and rotational contexts
  • Learn about angular kinematics and its applications in real-world scenarios
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Students of physics, mechanical engineers, and anyone interested in understanding the principles of work in linear and rotational systems.

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A) Questions, Equations & Attempts on answering

1) If I'm correct, for linear cases, Work= Fs,

F= Constant Force
s= Displacement

where Work can= negative if displacement ends up in the opposite direction, am I right?

2) Rotational Work= Fs

= Frφ

= τφ,

F= Constant Force
s= Displacement
r= Displacement for rotational work
φ= Resultant Angle
τ= Torque,and the case being considered,

220px-Work_on_the_lever_arm.jpg
.

Just confirming, say, at point F, this line, r's been spun -360°x10 times, if F increases, does that mean Rotational Work increases?

3) For 2), as r's been spun 360°x10 times counter clockwise, it won't be a negative work value would it?
 
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inv said:
Just confirming, say, at point F, this line, r's been spun -360°x10 times, if F increases, does that mean Rotational Work increases?

3) For 2), as r's been spun 360°x10 times counter clockwise, it won't be a negative work value would it?
If the force points in the direction of the displacement, then the work done will be positive; if it points opposite to the displacement, then negative.
 

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