Solving an Easy Physics Problem: Work Done on a Truck (9120 kg)

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Homework Help Overview

The discussion revolves around a physics problem involving a truck with a mass of 9120 kg that is decelerating from an initial speed of 28.8 m/s to a final speed of 13.8 m/s. Participants are tasked with finding the total work done on the truck during this process.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the appropriate method for calculating work done, with some suggesting the use of kinetic energy concepts. There is a focus on finding the initial and final kinetic energies and determining the change between them. Questions arise regarding the correct interpretation of work in relation to kinetic energy.

Discussion Status

There is an ongoing exploration of the relationship between work and kinetic energy, with various participants offering different perspectives on how to approach the problem. Some guidance has been provided regarding calculating initial and final kinetic energies separately, but no consensus has been reached on a definitive method.

Contextual Notes

Participants are navigating potential misunderstandings about the definitions of work and kinetic energy, as well as the implications of negative work in the context of energy loss. There may be confusion regarding the initial and final velocities used in calculations.

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"Easy" physics problem?

Homework Statement



A truck of mass 9120 kg is traveling along a level road at an initial speed of 28.8 m/s and then slows to a final speed of 13.8 m/s. Find the total work done on the truck.

Homework Equations



W=1/2*mv2

The Attempt at a Solution



W=1/2*(9120)*(13.8-28.2)2

this was wrong...
 
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I agree that kinetic energy is the right approach.
Find the KE initially. Find the KE after it slows down. Take the difference. Note that the truck loses energy, so it must be doing work on the road or negative work is done on it.
 


Work is not the kinetic energy, but rather the change in kinetic energy.
 


Rather than trying to combine the initial and final velocities into a difference of velocities, calculate the initial kinetic energy in its entirety, and do the same for the final kinetic energy. Once you have those, find the difference.
 

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