Hi, I am trying to figure out the power of a automobile collision.

Jan 2015
2
0
So to keep the math simple. a 1000 kg car hits a object while moving at 20 km/h. The impact lasts for 1 foot where the object is accelerated to 20 km/h.
1000kg(5.556 m/s – 0 m/s)/0.055s = 101018 Newton’s of force so because that impact was only for .3048 meters can I multiply newtons by meters and seconds to get 30790 Newton Meters multiplied by .055s for a final answer of 1693.45 newton m/s
Any help would be appreciated. Thanks.
 

ChipB

PHF Helper
Jun 2010
2,369
294
Morristown, NJ USA
... can I multiply newtons by meters and seconds to get 30790 Newton Meters multiplied by .055s for a final answer of 1693.45 newton m/s
Power is force times velocity, so the math is 30790 N-m divided by 0.055s to get 561211 N-m/s, or watts. However - this figure is valid only when the car is actually moving at 20 Km/Hr, which occurs only at the initial moment of impact. Over the course of the next 0.055 seconds it slows to 0 KPH, and consequently the power goes to zero during those 0.055s. Note that there is no such thing as "total power during the collision" - there is only instantaneous power and total energy of the collision, which is force times distance as you have already calculated = 30790 N-m.
 
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