Sports doctors are very concerned about brain injuries in contact sports. Brain injuries can occur if the head accelerates or decelerates at more than 50g, with injuries becoming serious or even life-threatening at 150g. Padded helmets are designed to reduce forces by lengthening the contact time. Suppose two 95 kg football players each running at 4.5 m/sm/s have a (illegal) head-to-head collision that brings both of them to a halt. A real collision of this sort is complex, but we can model it as a simple collision in which the force is constant for the duration of the collision. What magnitude force would decelerate each player at 75g? What is the minimum collision duration in ms for which their head accelerations would not exceed 75g? For players who are not wearing helmets, a true head-to-head collision has a duration of approximately 2.0 ms. In such a situation, what would be the head deceleration in g’s of these two players?

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