Question

A man is lifting a 15kg barbell repeatedly, from horizontal to a 30 degrees angle above the horizontal. The arm is 30 cm long, the biceps tendon is inserted at 4 cm distance below the elbow, the weight of the arm is 5 kg, and the center of mass for the arm is at 17 cm from the elbow. What is the force in the biceps during the exercise? How many times could he lift the barbell to consume the energy in a 300 Cal jelly donut (assume that only 25% of that energy is converted into mechanical work, while the rest is lost as heat)?

Answer 1