bme403_muslec3_2006

# bme403_muslec3_2006 - Statics-lecture 2 Another practical...

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Statics-lecture 2 Another practical application of statics is predicting joint reaction forces such as those involved in a patient moving onto a bedpan. This generally involves a patient using elbows and heels to elevate the hips. This is shown in the diagram below. The above model assumes body length equals leg length (30 cm) and neglects the weight of the legs. This makes the angle the body and legs make with the surface(bed) equal. The diagram is basically a free body diagram of the whole body. From this we can get: W = G1 + G2 from Σ Fy=0 and W 15 cos( θ ) = G2 60 cos( θ ) where θ is the angle the body or legs make with the surface. Solving we obtain G2=W/4 and G1=3W/4. To estimate the forces on the hip joint the free body diagram of the isolated body as shown below can be used.

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Muscle M corresponds to the gleuteus medius which can be assumed to span the tip of the isosceles triangle formed by the body and legs. To solve for M a moment balance is formed around the hip joint. M 10 sin( θ )+W 15 cos( θ
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