blushyak167Lv1
30 Oct 2021
Problem 13
Page 250
Section: Questions
Chapter 9: Static Equilibrium; Elasticity And Fracture
Textbook ExpertVerified Tutor
30 Oct 2021
Given information
Given: It is difficult to do sit-ups when your knees are bent than when your legs are stretched out.
Step-by-step explanation
Step 1.
Take the pivot at waist height, for a person doing crunches with the legs stretched we have the force of gravity doing torque counterclockwise, while the muscles of the abdomen do torque clockwise if the legs are stretched out the lever arm of the abdomen muscles is greater than lever arm of gravity, so it is easy to counteract the torque made by the force of gravity.
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