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This question was on my practice exam last week. However, I had no idea how to solve it, since plugging the variables into formulas left me with TWO unknown variables (no matter what formula), making any of them impossible to solve.. But there must be a solution. I'd be very grateful if you could give this a try?

A car accelerates from rest for 4 seconds, then maintains a constant velocity for 14 seconds. At the end of 18 seconds, it has traveled 1200 m. What is

a) its acceleration for the initial 4 seconds

b) the distance at which it stopped accelerating

now assume that the car decelerates at -12.5 m/s

c) how long does it take for it to come to a full stop, and after how many meters?

No idea, but I think one of:

v = v(initial) + at

v^2 = v(initial)^2 + 2a(x - x0)

or other one-dimensional equations?

I tried plugging the variables into every equation, but all of them yielded two unknown variables, making them impossible to solve.

Since I knew that in the second phase (phase with constant velocity) the initial and final velocities were the same, I did try replacing them with zero, as if I'd subtracted one from the other.. But that didn't work.

## Homework Statement

A car accelerates from rest for 4 seconds, then maintains a constant velocity for 14 seconds. At the end of 18 seconds, it has traveled 1200 m. What is

a) its acceleration for the initial 4 seconds

b) the distance at which it stopped accelerating

now assume that the car decelerates at -12.5 m/s

c) how long does it take for it to come to a full stop, and after how many meters?

## Homework Equations

No idea, but I think one of:

v = v(initial) + at

v^2 = v(initial)^2 + 2a(x - x0)

or other one-dimensional equations?

## The Attempt at a Solution

I tried plugging the variables into every equation, but all of them yielded two unknown variables, making them impossible to solve.

Since I knew that in the second phase (phase with constant velocity) the initial and final velocities were the same, I did try replacing them with zero, as if I'd subtracted one from the other.. But that didn't work.

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