7. 0.1/2 pointsI Previous Answers FRKestenCP1 9.P.069 My Notes During an Olympic

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7. 0.1/2 pointsI Previous Answers FRKestenCP1 9.P.069 My Notes During an Olympic clean-and-jerk weight lifting competition, a competitor lifted 250.5 kg. The competitor himself had a mass of 158 kg. Ultimately, the weight is all supported by the tibia (shin bone) of the lifter's legs. The average length of a tibia is 385 mm and its diameter (modeling it as having a round cross- section) is about 3.0 cm. Young's modulus for bone is typically about 2.0 x 1010 N/m2. (a) By how much would the lift compress the athlete's tibia, assuming that the bone is solid? 027 A weightlifter lifts a mass of 250.5 kg above his head. All of this weight is supported by the lifter's two tibias. The average length of a tibia is 385 mm and its diameter is 3.0 crm. The Young's modulus for bone is 2.0 × 1010 N/m2. we can use these data to calculate the distance his tibia is compressed upon lifting the weight. mm (b) Does this seem to be a significant compression? Yes No (c) Is it necessary to include the lifter's weight in your calculations? Why or why not? Yes, we need to include his weight because we are not interested in the compression due to extra weight. His tibia is initially compressed slightly due to his weight; we've assumed the value of 385 mm does not include that initial compression. No, we do not need to include his weight because we are interested in the compression due to extra weight. His tibia is initially compressed slightly due to his weight; we've assumed the value of 385 mm includes that initial compression.

Explanation / Answer

given, lift, m = 250.5 kg

mas sof competitor, M = 158 kg

length of tibia, l = 385 mm

diameter, d = 3 cm

Youngs modulus, Y = 2*10^10 N/m^2

a. let compression be dl

then from hookes law

stress/strain = Y

(m)g*4*l/pi*d^2*dl = Y

dl = 0.066922 mm

b. this compression is really insignificant

c. No, we donot need to consider his wight because we are interested in the compression of the bione due to just th elift and not his weight

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