Final answer:
The power spent by the horse is 12,500 watts and approximately 16.77 horsepower.
Step-by-step explanation:
The power spent by the horse can be calculated using the formula: power = force * velocity. In this case, the force exerted by the horse is 500 N and the velocity of the horse is 25 m/s. So, the power spent by the horse is equal to 500 N * 25 m/s, which is equal to 12,500 watts.
To convert this value to horsepower, we can use the conversion factor: 1 horsepower = 746 watts. So, the power spent by the horse is equal to 12,500 watts / 746 watts/horsepower, which is approximately equal to 16.77 horsepower.