During vigorous downhill hiking, the force on the knee cartilage (the medial and

Question

During vigorous downhill hiking, the force on the knee cartilage (the medial and lateral meniscus) can be up to eight times body weight. Depending on the angle of descent, this force can cause a large shear force on the cartilage and deform it. The cartilage has an area of about 10.0cm2 and a shear modulus of 12.0MPa . Part A If the hiker plus his pack have a combined mass of 113kg (not unreasonable), and if the maximum force at impact is 8.00 times his body weight (which, of course, includes the weight of his pack) at an angle of 12.0 degrees with the cartilage, through what angle (in degrees) will his knee cartilage be deformed?

Explanation / Answer

m=113*8=904 Kg

F=mg=904*9.8=8859.2 N

F'=Fsin(12)=1841.93 N

tan(phi)=1841.93/(11 x10^-4*12x10^6)=0.1395

So phi=7.944 degrees

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