The horse is accelerating at a rate of 1m/s^2.
Its velocity is 3m/s in the first second.
It’s velocity is 4m/s in the next second, and 5m/s in the third second.
Since the velocity is increasing at a rate of 1m/s and acceleration is defined as the change in velocity, therefore the acceleration is 1m/s^2.
Let me know if you have any questions.
