How Do You Calculate Dragster Deceleration Time and Distance?

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Homework Help Overview

The discussion revolves around calculating the deceleration time and distance for a dragster that accelerates and then decelerates to a stop. The problem involves kinematic equations and the relationships between acceleration, time, and distance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply kinematic equations to find the distance covered during acceleration and the time taken during deceleration. Some participants suggest the need for additional equations to relate initial and final velocities with acceleration and time.

Discussion Status

Participants are engaging in a constructive dialogue, offering guidance on the application of formulas and encouraging the original poster to explore further calculations. There is recognition of the need for multiple equations to solve for unknowns in the deceleration phase.

Contextual Notes

The original poster expresses difficulty in determining viable formulas for the deceleration phase, noting that certain variables are not specified. There is an emphasis on the expectation that the original poster will contribute their own attempts to the discussion.

Casey Wilson
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Homework Statement



- A Dragster at the starting line accelerates at 8 m/s^2 to the finish line. If it took 4.6 s, how long is the track?
- The Dragster deccelerated to a stop in 100m. How long did it take?

Homework Equations



x = 0 + 1/2at^2

The Attempt at a Solution



The first part of the questions I got x = 84.64m using the above equation.
For the life of me, I cannot figure out how to get anything viable for other formulas, when v or a is not specified for decceleration (read: Part 2).
 
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Hello casey, welcome to PF :)

Same formula, but now the initial speed isn't zero. And x isn't the unknown, because it's a given. The unknown is a. And t of course. So you'll need another equation. Something relating v initial, v final, t and a.

From there (with v final = 0) you'll find t. (two equations with two unknowns)

You'll do fine.
 
BvU said:
Hello casey, welcome to PF :)

Same formula, but now the initial speed isn't zero. And x isn't the unknown, because it's a given. The unknown is a. From there (with v final = 0) you'll find t. (two equations with two unknowns)

You'll do fine.

I think I see where you are coming from.
Thank you for the quick reply and the welcome.

I missed the second part of your answer. I think I got it figure out. Thank you!
 
Ah, some PF culture here: you do the work, helpers help. So jot something down and solicit comments/assistance !
You'll need this other equation anyway (it's no big deal, you must have seen it come by already at some point in the lectures/testbook) to determine the speed when the braking starts.

Hint: check out the formulas here (where it says three key variables)
 
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