Calculating Car Acceleration: Kinematic Equations

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Homework Help Overview

The problem involves calculating the acceleration of a car that comes to a stop after applying brakes for a specified time and distance. The context is kinematics, specifically focusing on the application of kinematic equations to determine acceleration.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply a kinematic equation to find acceleration but expresses uncertainty about the next steps and the appropriateness of the equation used. Some participants confirm the use of the correct equation and suggest simplifying the mathematical components. Others highlight the nature of acceleration in this context, noting that it is negative due to deceleration.

Discussion Status

The discussion is ongoing, with participants providing guidance on mathematical simplification and clarifying the terminology related to acceleration and deceleration. Multiple interpretations of the problem are being explored, particularly regarding the definition of acceleration in this scenario.

Contextual Notes

The original poster's confusion about the kinematic equation and the nature of acceleration indicates a potential gap in understanding the relationship between distance, time, and acceleration in the context of braking. There is also a reiteration of the problem statement, which may suggest a need for clarity or emphasis on the key elements of the scenario.

helpme2012
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Homework Statement



You are driving your car and you heavily apply the brakes for a period of 2.1 seconds. The car keeps moving for a distance of 14.6m before it completely stops.

What is the acceleration (in m/s2) experienced by the car? Is it truly "acceleration"?

Homework Equations



5 kinematic equations

The Attempt at a Solution


I was using this : Δd=VfΔt-0.5aΔt2

14.6=0(2.1)-0.5a(2.12)
14.6= 0-0.5a(4.41)

I don't know what to do after that, I don't know what to do with the part of the equation with the acceleration. Am I even using the right kinematic equation?
 
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You are using the right one! Note how you have a single equation with just one unknown, a - which is exactly what you're after.
So much for the physics part, you need to pull out your mathematical skills now and solve the equation. First, try simplifying 0.5 * 4.41 and 0 - ...
 
Notice the "0- " part. The acceleration will be negative. In everyday language we would call that "deceleration" but, technically, it is still a type of "acceleration".
 
helpme2012 said:

Homework Statement



You are driving your car and you heavily apply the brakes for a period of 2.1 seconds. The car keeps moving for a distance of 14.6m before it completely stops.

What is the acceleration (in m/s2) experienced by the car? Is it truly "acceleration"?


Homework Equations



5 kinematic equations

The Attempt at a Solution


I was using this : Δd=VfΔt-0.5aΔt2

14.6=0(2.1)-0.5a(2.12)
14.6= 0-0.5a(4.41)

I don't know what to do after that, I don't know what to do with the part of the equation with the acceleration. Am I even using the right kinematic equation?
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