The problem involves a car that begins decelerating from an initial velocity of 20 m/s and travels a distance d before coming to a stop. The task is to determine the car's velocity at the halfway point, d/2.
The discussion includes various interpretations of the problem, with participants offering different methods and questioning the necessity of time in the solution. Some guidance has been provided regarding relevant equations, but no consensus has been reached on a single approach.
Participants note the absence of information regarding acceleration, which complicates the problem-solving process. There is an emphasis on working with the given initial conditions and the relationship between variables.
Lizi said:Homework Statement
A car moving at 20m/s starts decelerating, travels distance d, and stops. Find the car’s velocity at distance d/2.
Homework Equations
The Attempt at a Solution
my brain is fried. I feel like I’m missing something obvious but I just don’t get it.
neilparker62 said:It was a bit of a brain 'fry' !
Time 'reversing' so that we have acceleration from 0 m/s instead of deceleration from 20 m/s:
$$ d = ½at^2 ⇒ \frac{d}{2} = ½a\left({\frac{t}{\sqrt{2}}}\right)^2 ⇒v=\frac{at}{\sqrt{2}}$$
at = ?stockzahn said:But since you don't know ##a## you can't obtain ##t##, so you stick with two unknowns. I think the question should be solved independent of the time ...