Impulse of ForceThe product of average force and the time it is exerted is called the impulse of force. From Newton's second lawthe impulse of force can be extracted and found to be equal to the change in momentum of an object provided the mass is constant:

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Minimizing Impact ForceThe process of minimizing an impact force can be approached from the definition of the impulse of force:
An impact which stops a moving object must do enough work to take away its kinetic energy, so extending the distance moved during the collision reduces the impact force. 
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Airplane and DuckEstimate the average impact force between an airliner traveling at 600 mi/hr and a 1 pound duck whose length is 1 foot. This is an example of the use of impulse of force.How much impact force? 
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Airplane & Duck Force EstimateFor the airplane and duck force estimate, the mass of the duck is needed, but the weight in the U. S. Common system of units is given. The mass is
Jack Elrod in his Mark Trail comic strip (2/27/2000) says "If an aircraft strikes a big bird at a speed of 500 MPH, the impact will be about 25 tons." He is pretty well on target, considering the above model for a headon collision with a medium sized bird. The comment is in a strip on bird collisions in Israel, which has the world's largest density of migrating birds during the migration season. Since 1972 they have logged 1,282 "bird hits" with fighter aircraft, 696 with helicopters, and 637 with transport planes and light aircraft. 
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Airplane & Duck EstimatesFor the airplane and duck force estimate, the mass of the duck is determined, but the change in velocity and time of collision must be estimated in order to estimate the average impact force.
The change in
velocity of the
duck is estimated to
be 600 mi/hr = 880 ft/s by assuming a head on collision, assuming that the duck is riding with the airliner after the collision, and assuming that the duck's velocity is negligible compared to that of the
airliner, the
"hovering duck"
approximation. 
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Airplane & Duck Collision ForceAs a variation on the airplane and duck problem, change the mass of the bird and speed of the aircraft. Enter a length of the bird for estimation of the impact time. 
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