Finding the magnitude of acceleration in 2D motion

[Dano1337]

Homework Statement

A car moving due south at 20.0 m/s enters a highway cloverleaf. The car will exit the cloverleaf to merge with westbound traffic traveling at 29.0 m/s.

The time between entering the cloverleaf and exiting to merge with westbound traffic is 20.7 s. What is the magnitude of the average acceleration of the car?

For the units, use a ^ to indicate an exponent.

Your answer should have one digit after the decimal place.

Homework Equations

magnitude eq = v = sqrt (x^2)+(y^2)
average a = change in velocity / change in time

The Attempt at a Solution

1. sqrt ((20^2)+ ((29^2)) = 35.2 m/s
2. 35.2 / 20.7 = 1.7 s
any help or advice on where I'm going wrong would be very much appreciated. [/B]

 

[olivermsun]

Check the units on your last line (2)?

 

[haruspex]

average a = change in velocity / change in time

Correct.

magnitude eq = v = sqrt (x^2)+(y^2)

It says nothing about change in speed.

magnitude of the average acceleration

Magnitude of change of velocity is not the same as change of magnitude of velocity.