9-9 CHAPTER 9 Work and Kinetic Energy 23. In Example 9.9 in the textbook, a compressed spring with a spring constant of 65 N/m expands from Fo =-12 cm =-0.12 m to its equilibrium position at x, 0m. a. Graph the spring force (FSp)s from x -0.12 m to x1= 0 m. (Peg,(N) 7.8 Potenti 0-x (m) 0 -.12 -09-06 -03 b. Use your graph to determine AK, the change in a cube's kinetic energy when launched by a spring that has been compressed by 12 cm. c. Use your result from part b to find the launch speed of a 100 g cube in the absence of friction. Compare your answer to the value found in the Example 9.9.

Answer both or NONE question 1 -  For exercise, an athlete lifts a barbell that weighs 400 N from the ground to a height of 2.20 m at a constant speed in a time of 1.60 s. What is the metabolic power, in kW (kiloWatts)?  Your answer needs to have 2 significant figure, including the negative sign in your answer if needed. Do not include the positive sign if the answer is positive. No unit is needed in your answer, it is already given in the question statement.   Question 2 -  The metabolic power for typing is 150 W for Lili, not a lot as you know probably. How long does it take to burn off the energy in a slice of apple pie, which energy content is 1680 kJ (400 food calorie), in minutes?  (Try to stay active, working/studying in front of a computer is not the best exercise you can do for your body.)

4. A 2.5 kg object falls vertically downward in a viscous medium at a constant speed of 2.5m/s. How much work is done by the force the viscous medium exerts on the object as it falls 80.0cm? A. -2.0 x 10 J B. -39 J C. 39 J D. 2.0 × 10 J E. O J