Question

What is the acceleration of an object if it goes from a velocity of +25 m/s to rest in 5.0 s?

A. 5 m/s
B. +5 m/s
C. 25 m/s
D. +25 m/s

Answer 1

The answer should be -5 m/s since it decelerated from 25 m/s to rest.
I'm not sure if you just forgot to add the negative sign to A

Answer 2

Acceleration = (change in speed) / (time for the change)

Change in speed = (speed at the end) - (speed at the beginning)

= (zero) - (25 m/s)

= -25 m/s .

Acceleration = (-25 m/s) / (5 sec) = -5 m/s² . <===

None of the choices says this.