Find Time for TBI Injury Risk: Hardwood vs Carpeted Floors

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The discussion centers on calculating the risk of traumatic brain injury (TBI) for a child falling from a bed onto hardwood versus carpeted floors. Participants emphasize the importance of determining the child's head speed upon impact using kinematic equations, without needing the fall time. The conversation highlights the need to calculate deceleration and impact duration to assess injury risk accurately. A suggestion is made to learn and memorize kinematic motion equations for better understanding. Overall, the focus is on applying physics principles to evaluate safety in different flooring scenarios.
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Homework Statement


Traumatic brain injury such as concussion results when the head undergoes a very large acceleration. Generally, and acceleration less then 800 m/s^2 lasting for any length of time will not cause injury, whereas an acceleration greater then 1000 m/s^2 lasting for a least 1 millisecond will cause injury. suppose a small child rolls off a bed that is 0.40 m above the floor. if the floor is hardwood, the child's head is brought to rest in approximately 2.0 mm. if the floor is carpeted, this stopping distance is increased to about 1.0 cm. Calculate the magnitude and duration of the deceleration in both cases, to determine the risk of injury. Assume the child remains horizontal during the fall to the floor. Note that a more complicated fall cound result in a head velocity greater or less than the speed you calculate


Homework Equations


Vf=at+Vo


The Attempt at a Solution


a=-9.8 m/s^2
t=?
Vo=0
Xo=0
Xf=.4m

The only problem I have with this question is, finding time, and without time I couldn't really start. so any tips on how to start this? I don't want the answer really this is my first year of physics and I would love to understand this.
So if someone could teach me how to solve for time that would be great!
 
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You first need to find the speed of the child's head at the instant it hits the floor. You can do this without knowing the time of the fall, by using another kinematic equation. then move on to the 2nd step to calculate the acceleration during , and duration of , the impact.

Welcome to PF!
 
PhanthomJay said:
You first need to find the speed of the child's head at the instant it hits the floor. You can do this without knowing the time of the fall, by using another kinematic equation. then move on to the 2nd step to calculate the acceleration during , and duration of , the impact.

Welcome to PF!

I don't know many Equations so would you mind showing me the way?

and thank you and congrats on 4,444 posts :)
 

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