Why Is Deceleration Expressed as a Positive Value in Physics Problems?

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Homework Help Overview

The discussion revolves around a physics problem involving a car decelerating to a stop. The original poster presents a scenario where a car traveling at 10 m/s applies brakes and comes to rest over 16 seconds, leading to a question about the representation of deceleration as a positive value.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between acceleration and deceleration, questioning why deceleration is expressed as a positive value despite being derived from negative acceleration. Some discuss the conversion of negative acceleration to a positive deceleration value.

Discussion Status

Participants are actively engaging in clarifying the terminology and concepts related to acceleration and deceleration. There is a recognition of the distinction between negative acceleration and positive deceleration, with some expressing agreement on the understanding of these terms.

Contextual Notes

There is a discussion about the conventions used in physics regarding the signs of acceleration and deceleration, with some participants noting that negative acceleration can be referred to as deceleration, while positive acceleration may not typically be described as negative deceleration.

TheShiny
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Homework Statement


"A car is approaching traffic lights. The car is traveling with speed 10ms-1. The driver applies the brakes to the car and the car comes to rest with constant deceleration in 16s. Modelling the car as a particle, find the deceleration of the car."


Homework Equations


v = u + at


The Attempt at a Solution


[STRIKE]s =[/STRIKE], u = 10ms-1, v = 0ms-1, a = ?, t = 16s

v = u + at
0 = 10 + 16a
a = -10 ÷ 16
a = -0.625ms-2

The answer given is 0.625ms-2. Why is the answer positive and not negative?
 
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If the particle (the car) is slowing down it would have negative acceleration.

So, to go from acceleration to deceleration multiply by -1.

Therefore the deceleration would be -1 * -0.625 = 0.625

Is that why the answer is positive or have I misunderstood?
 
The car's acceleration is -0.625 units, its deceleration is 0.625 units :) Game of words
You have understood correctly.
 
Last edited:
As lendav_rott said,
Negative acceleration is simply deceleration and | positive acceleration can be negative deceleration(Can be,but this is rarely used or never used(in my experience))
 
Last edited:

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