Final answer:
To determine the bone stretch of the lower performer in a circus act, Hooke's Law and the elasticity of bone are used, requiring a calculation based on the force (which is three times the performer's weight plus the weight itself) and the properties of the femur bone.
Step-by-step explanation:
During a circus act where one performer swings upside down hanging from a trapeze and holds another performer by the legs, we are asked to determine how much the femurs in the upper legs of the lower performer stretch under stress. Since the upward force on the lower performer is stated to be three times her weight, we can calculate this stretch using Hooke's Law and the modulus of elasticity for bone. Given the mass of the performer is 60.0 kg, we first calculate the force exerted on her bones which is the sum of her weight and the upward force, taking into account that weight is mass times the acceleration due to gravity (9.8 m/s2). After finding the force, we then apply the formula for deformation under stress which involves the force exerted, the length of the bone, the cross-sectional area, and Young's modulus for bone. This type of problem is an application of concepts of elasticity, stress, and strain from the field of mechanics, a branch of Physics