Work and motion strategies to a problem

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Homework Help Overview

The problem involves understanding the work-energy theorem in the context of a ball thrown into the air. The original poster discusses calculating the work done by gravity at the ball's maximum height, given its mass and initial velocity.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the work-energy theorem and kinematic equations to find the work done by gravity. Some participants question the values used in the calculations, particularly the mass and the force derived from it.

Discussion Status

The discussion is ongoing, with participants clarifying the values used in the calculations and addressing discrepancies in the mass of the ball. There is no explicit consensus yet, but the dialogue is focused on correcting assumptions and understanding the problem better.

Contextual Notes

There is a noted confusion regarding the mass of the ball, with one participant mistakenly using a different value in their calculations. Units for distance and force are also questioned, indicating a need for clarity in the problem setup.

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Homework Statement



So the problem is getting at a basic understanding of the work energy theorem, and just asks for the work done by gravity at a ball's max height if the ball (with mass 0.25 kg) is thrown into the air with initial velocity of 30 m/s. using W=change in KE, the answer is -112.5 J

But if I use the formula vf^2 = vi^2 + 2ad, to determine d, I get d as approx. 46, and so W=294 x 46 = 13524 J ??



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The Attempt at a Solution

 
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Where did 294 come from? And 46 what? (units!)
 
right, 46 meters. and the 294 (N) was the force calculated as mxa = 30 kg x 9.8 m/s2
 
You said the mass is .25 kg, not 30 kg
 
haha, right. not sure why my brain did that.
 

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