help with math ?'s please?

Question

Comparing Accelerations
How does the acceleration of an object traveling eastward slowing down at a rate of 5 m/s2 compare to the acceleration of a second object traveling westward speeding up at a rate of 5 m/s2?

and


At the top of a hill, a rollercoaster is traveling with a velocity of 2.0 m/s downward, but accelerates to 15.0 m/s by the time it reaches the bottom of the hill. If it took 2.0 seconds to reach the bottom of the hill, what was its acceleration?

and

What is the final velocity of an object starting from rest which accelerates at 17.0 m/s2 northward for 3.0 seconds?

Answer 1

1.) They are behaving as if an accelerative force(such as a gravitational force) is acting on both of them from the west.

2.) a = (v(final) - v(zero))/t = (15.0 - 2.0)/2.0 = 6.5 m/s^2

3.) v = at = (17.0)(3.0) = 51m/s