Answer:
The acceleration of the horse as it came to a stop is
.
Step-by-step explanation:
Given that,
Initial speed of the horse and rider, u = 21 m/s
It finally comes to rest, v = 0
The horse slows down for 52 m with constant acceleration before it stops.
We need to find the acceleration of the horse as it came to a stop. Let a is the acceleration. We can find it using third equation of motion as :
We need to find the acceleration of the horse as it came to a stop. Let a is the acceleration. We can find it using third equation of motion as :

So, the acceleration of the horse as it came to a stop is
. Negative sign shows deceleration.