# Constant acceleration

## Homework Statement

A speeding car has instantenous velocity of 1 m/s when a stopwatch reads 10 seconds. It has constant acceleration of 2 m/s^2.
What is the cars speed when it reaches the stopwatch reads 12 seconds.

## Homework Equations

x= (Vinitial)(DeltaT) + 1/2(a09deltaT)^2
I think this is the right equation for constant acceleration...

## The Attempt at a Solution

(1.0m/s)(2seconds) + 1/2(2m/s/s)(2)^2
2 + 4
= 6 m/s

This is a problem in my textbook, and the answer they give is 5 m/s. Am i using the wron equation? Or what am i doing wrong?

billy_joule
You are using an equation to find a distance 'x', but you need a velocity.

## The Attempt at a Solution

(1.0m/s)(2seconds) + 1/2(2m/s/s)(2)^2
2 + 4
= 6 m/s

Should be
(1 m/s)(2 seconds) + 1/2(2 m/s/s)(2 s)^2
2 m + 4 m
= 6 m

That's the distance travelled between 10 and 12 seconds, not what you are looking for... You need a different equation.

I'm stumped. Is it one of those other constant acceleration equations? Whenever I look at them, it always seems like I'm not looking at the right one because it has more variables than what I'm given in the question

SteamKing
Staff Emeritus