Work, Energy, and Power Test Review

He was asked to determine whether a vehicle built to

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Jim is interviewing for a new job as test driver. He was asked to determine whether a vehicle built to test the effects of high accelerations on people is safe. The car, with mass 2000 kg, moving at a speed of 20 m/s runs into a spring that compresses the air in a cylinder and stops the car in 0.30 m. The 70 kg passenger stops in the same distance due to the force of shoulder straps and seat belts on her body. What is the spring constant (DON’T FORGET THE SPRING IS STOPPING THE CAR AND THE PERSON…)? 9.2x10 6 N/m What is the Elastic Potential energy of the spring? 414,000 J How much work does the spring do? 414,000 J What is the force of the spring on the car/person system? 1.38x10 6 N Determine the average force of these restraints on the person during the stop. 46,667 N What is the Power output of the spring on the system if the stop takes 0.7 s? 591,428 W What would happen to the spring constant if we doubled the mass of the car? 4) Jim continues his new job as a test driver. The company asks him to find the coefficient of friction between their new tires and the road. He decides to set up an experiment. He travels in his car at a velocity of 30 m/s and slams on the brakes. The car comes to a stop over a distance of 50 m.

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• Fall '12
• Lahm

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