# Average Force Formula

The average force is the force exerted by a body moving at a defined rate of speed (velocity) for a defined period of time. The word 'average' is used to indicate that this is not an 'instantaneous' or precisely measured velocity. Thus, average Force is equal to the mass of the body multiplied by the average velocity over the defined time.

F = m (v_{f} - v_{i})/t

F = force

m = mass

v_{avg} = average velocity

v_{f} = final velocity

v_{i} = initial velocity

t = time

Average Force Formula Questions:

1) A dog that weighs 10 kg chases a car for 12 seconds at a velocity of 5 m/s. What is the average force for the dog?

Answer: The mass, m = 10 kg. The dog's average velocity, vavg = 5m/s; the time, t = 12 seconds.

F = m (v_{f} - v_{i})/t

F = 10 kg (5 m/s - 0 m/s) / 12 sec

F = 50 kg m/s / 12 sec

F = 4.166 kg m/s^{2} = 4.166 Newtons

2) A 5kg ball is rolled for 15 seconds at an average velocity of 7 m/s. What is its average force?

Answer: The mass of the ball, m = 5 kg. The time t = 15 s. The v = 7 m/s.

F = m (v_{f} - v_{i})/t

F = 5 kg(7 m/s)/15 s

F = 35 kg m/s / 15 s

F = 2.33 kg m/s^{2}

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