# Vectors and Acceleration in a Straight Line

What is the change in velocity when:
a) 6.0 m/s becomes - 15 m/s
b) 5.0 m/s East becomes 15 m/s West

My doubt is mainly the notation: How I should answer, here is my try:

a) -9 m/s with 180 degrees change in direction
b) 9 m/s with from direction bearing 90 degrees to 270 degrees

And: A baby buggy rolls down a ramp which is 15 m long. It starts from rest and accelerates uniformly and takes 5.0 seconds to reach the bottom:
a) Average Velocity: 15 /5 = 3 m/s

Now, b asks for the velocity at the bottom. I don't know how to calculate the velocity without the acceleration, which is asked in question c)

c) s = ut x 1/2at^2
a = 1.2 m/s^2

and then

b) v = u + at
v = 6 m/s

Anyone can teach me how to get the velocity without the acceleration and with the notation in the first question?

Thanks,
Peter

verty
Homework Helper
You can find the final velocity with this formula (only when acceleration is constant):

s = t(u+v)/2

Aw, yea that's right, thanks.

And what about my answers to the first question? Think they are O.K?