Final answer:
The horse's average acceleration can be calculated by converting the given velocity to meters per second, then using the formula for acceleration (change in velocity over change in time). The average acceleration is found to be approximately 4 m/s², which doesn't match the provided multiple-choice options.
Step-by-step explanation:
The question is asking us to calculate the average acceleration of a horse that starts from rest and reaches a velocity of 70 km/hr in 5 seconds. To find the acceleration, we need to first convert the velocity to meters per second since acceleration is measured in meters per second squared (m/s²). We know that 1 km/hr is equivalent to 1/3.6 m/s. Therefore, 70 km/hr is equal to 70/3.6 m/s, which is approximately 19.44 m/s.
Now, we can use the formula for average acceleration, which is:
a = (Δv) / (Δt)
Δv is the change in velocity, and Δt is the change in time. Since the horse starts from rest, the initial velocity is 0, and the final velocity is 19.44 m/s. The time taken to reach this velocity is 5 seconds, so:
a = (19.44 m/s - 0 m/s) / (5 s) = 3.888 m/s²
This value must be rounded to the nearest whole number since the options are given in whole numbers. Therefore, the horse's average acceleration is approximately 4 m/s², but since this option isn't provided in the multiple choice, we might need to check our calculation again or discuss with the instructor about the discrepancy in the given options.