You are out running and the first mile takes you 10 minutes. the second mile takes you 20 minutes. this is an example of negative acceleration. velocity. instantaneous speed. positive acceleration.

If Equal distance is traveled in equal interval of time then it is known as uniform motion in which velocity of object will remain same.

Then if distance covered will be same and the time taken to cover same distance is decreasing then it shows that speed is increasing with time due to which it took less time to cover same distance. This is also known as positive acceleration.

Now if the distance covered will be same and time taken to cover same distance is increasing then it shows that speed is decreasing with time due to which it took more time to cover the same distance. This is also known as negative acceleration.

Now in the above case it is given that the first mile takes you 10 minutes. The second mile takes you 20 minutes. So the time taken is increasing while we cover same distance so this is an example of Negative Acceleration