7.89. Set Up: For part (a), apply with which results in For parts (b) through (d), the maximum force F exerted by the air bag is expressed as Solve: (a) Solving for the spring constant gives (b) Use the expression in part (a) to replace k in the relation (c) (d) The expression in part (b) gives (e) Reflect: A safer design requires a larger distance This could be accomplished by extending the gas, brake and clutch pedals so that the driver could sit further away from the steering wheel or by decreasing the stiffness k of the airbag. A stiffer air bag would increase k and and thus make the system less safe. 7.90. Set Up: To find the maximum speed, start with Let the initial displacement from equilibrium, and then and Substituting and solving for the maximum speed, we obtain For the maximum acceleration, noting that we have The instrument has Solve: (a) Maximum speed: Maximum acceleration: (b) Reflect: No. The maximum speed occurs at when the object passes through the equilibrium position. The
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This note was uploaded on 03/06/2009 for the course PHYS 114 taught by Professor Shoberg during the Spring '07 term at Pittsburg State Uiversity.