(adsbygoogle = window.adsbygoogle || []).push({}); 1. The total cross-sectional area of the load-bearing calcified portion of the two forearms bones (radius and ulna) is approximately 2.16cm^2. During a car crash, the forearm is slammed against the dashboard. Tha arm comes to rest from an initial speed of 81.9km/h in 7.72 s. If the arm has an effective mass of 1.88kg what is the compressional stress on the arm? Answer in units of Pa.

2. Stress=F/A,

additional

F=ma

Vf=Vo+at

3.

Conversions

A=2.16cm^2*1m^2/10^4cm

=2.16e-4m^2

Vo=81.9km/h*(1hr/60mins)(1min/60s)(1000m/1km)

=22.75m/s

F=ma

a=(Vf-Vo)t=-2.94689.

I assumed I could make it positive since the problem's context is in forward motion not retardation.

F=1.88kg*2.94689

=5.540kg*m/s^2

P=F/A

P=5.540kg*m/s^2/2.16e-4

=25.648.8677N/m^2= same in Pa.

I feel like I put in the appropriate conversions and formulas but when I plug in the answer, I'm told I am wrong. Does it have to do with the fact that it mentions "two forearm bones" in the beginning? If it is, where do I half the cross sectional area?

I hope I'm not too far off.

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# Homework Help: Elastic Deformation through compression (stress)

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