A 40kg miniature horse runs west at 8 m/s . What is the force of impact if it hits a fence and comes to a sudden stop in 0.5s?

640 N

Explanation:

Given :

Mass of horse, m = 40kg

initial speed of horse, u = 8 m/s

final speed of horse, v = 0 m/s  (because horse comes to a sudden stop)

time taken to stop, t = 0.5 s

recall that acceleration = change in speed / time taken for the change

or

a = (v - u) / t     (substituting the above values)

a = (0 - 8) / 0.5

a = -16 m/s²   (i.e it is a deceleration of 16 m/s²)

since we are not concerned about the direction of the force, we can simply use the absolute value of acceleration which is a = 16 m/s²

also recall that

Force = mass x acceleration

F = ma    (substituting the values above)

F = 40kg x 16 m/s

F = 640 N

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