1. [0/4 Points] DETAILS PREVIOUS ANSWERS OSCOLPHYS2016ACC 7.4.P.022. MY NOTES A 5.50 x 105 kg subway train is brought to a stop from a speed of 0.500 m/s in 0.400 m by a large spring bumper at the end of its track. What is the force constant k of the spring (in N/m)? (Enter a number.) 0.32 X N/m Submit AnswerASK YE PREVIOUS ANSWERS OSCOLPHYSZMGACC 7.5.P.025. (a) How high (in m) a hill can a car coast up (engine disengaged) if friction is negligible and its initial speed is 86.0 krnfh? (Enter a number.) 29 09 y m 4. [2.66M Points] (b) If, in actuality, a 750 kg tar with an initial speed of 86.0 krn/h is observed to meet up a hill tu a height 16.0 m abuve its starting point, how much thermal energy (in J) was generated by frittion'.' (Enter a number.) 962i15 J J ((3 What is the average force uf frittion (dawn the slope) if the H\" has a slope 2.5D above the horizontal? (Enter yuur answer in N. Enter a number.) 220.37 x N 7. [-/4 Points] DETAILS OSCOLPHYS2016 7.6.WA.052. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A 5.36 kg object falls freely (ignore air resistance), after being dropped from rest. Determine the initial kinetic energy (in ]), the final kinetic energy (in J), and the change in kinetic energy (in ]) for the following. (a) the first meter of the fall initial kinetic energy final kinetic energy change in kinetic energy (b) the second meter of the fall initial kinetic energy final kinetic energy UU change in kinetic energy Additional Materials Reading Submit Answer 8. [-/4 Points] DETAILS OSCOLPHYS2016ACC 7.7.P.039. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) Find the useful power output (in W) of an elevator motor that lifts a 2500 kg load a height of 30.0 m in 12.0 s, if it also increases the speed from rest to 4.00 m/s. Note that the total mass of the counterbalanced system is 10,000 kg-so that only 2500 kg is raised in height, but the full 10,000 kg is accelerated. (Enter a number.) W (b) What does it cost (in cents), if electricity is $0.0900 per kW . h? (Enter a number.) cents +9. [-/4 Points] DETAILS OSCOLPHYS2016ACC 7.8.P.047. MY NOTES (a) What is the efficiency of an out-of-condition professor who does 2.10 x 10 J of useful work while metabolizing 510 kcal of food energy? (Enter your answer as a percentage. Enter a number.) % (b) How many food calories (in kcal) would a well-conditioned athlete metabolize in doing the same work with an efficiency of 25%? (Enter a number.) kcal Submit Answer 10. [-/4 Points] DETAILS OSCOLPHYS2016 7.9.P.060. MY NOTES (a) Calculate the force (in N) the woman in the figure below exerts to do a push-up at constant speed, taking all data to be known to three digits. (You may need to use torque methods from a later chapter.) m = 53 kg CG W 0.88 m Freaction 1.46 m N (b) How much work (in ]) does she do if her center of mass rises 0.260 m? (c) What is her useful power output (in W) if she does 21 push-ups in 1 min? (Should work done lowering her body be included? See the discussion of useful work in Work, Energy, and Power in Humans.) W