Motion: Solving problems using equations

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Homework Help Overview

The discussion revolves around a physics problem involving motion, specifically the calculation of distance covered by a sprinter accelerating from rest and the time taken to complete a 100m sprint. The original poster expresses uncertainty about their calculations and the correctness of textbook answers.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply the kinematic equation for distance but questions the accuracy of their calculations and the textbook answers. Participants clarify the initial speed and point out a mistake in the calculation method.

Discussion Status

The discussion is active, with participants providing hints and clarifications. The original poster acknowledges a mistake in their approach, indicating a productive direction in understanding the problem.

Contextual Notes

The original poster expresses concern about potentially misunderstanding the problem and the correctness of the textbook answers, which may influence their confidence in solving the problem.

tryintosurviv
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Im sorry if this is in the wrong area ! and I know that this is the easiest question in the history of physics but I need help. I think some of the answers in the back of the text are wrong but I might be just the biggest idiot on the face of the Earth so feel free to point that out. anyways ...

Homework Statement


If 100m sprinters accelerate from rest for 3.5 s at 2.8 m/s (squared) , how far have they ran to this point ? How long will it take them to complete the 100m sprint , assuming they maintain their speed the rest of the way ?

Homework Equations



d= v1t + 1/2a t (squared)

I think ?

The Attempt at a Solution



= 3.5 + 1/2 (2.8)(3.5) squared
= 3.5 + 1/2 (2.8)(12.3)
=3.5 + 34.2 divided by 2
= 3.5 + 17.2
= 20.7 sorry I don't have the division sign or superscript

and I can't do the rest of the question without having the first answer correct. The text says the answer is 17 m


HELP ! Please help a huge idiot
 
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Hint: What's the initial speed? (What you call v1.)
 
Isn't it 0 m/s ? It says from rest
 
tryintosurviv said:
Isn't it 0 m/s ? It says from rest
Exactly! Do you see what's wrong with your calculation now?
 
OH wow that's great. I was adding instead of multiplying ! Thanks
 

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