A ball rolling across a field with an acceleration of -0.5 m/s rolls 12.5 m and then comes to a stop after 8 seconds.

What was the ball's initial speed?

1 answer

deceleration rate * time = Initial speed
= 4 m/s.

It should come to rest after rolling a distance (average speed)*(time) = 16 meters.

You have been given more infrmation that you need, and some of it is inconsistent.

Your deceleration rate also has the wrong units. m/s is not correct units for acceleration