6. [2.861571 Points] I DETAILS l PREVIOUS ANSWERS OSCOLPHY52016ACC 7.3.P.017. MV NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) How much gravitational potential energy (in J) (relative to the ground on which it is built) is stored in an Egyptian pyramid, given its mass is about 7 x 109 kg and its center of mass is 30.0 m above the surrounding ground? (Enter a number.) 20580000 X J (b) What is the ratio of this energy to the daily food intake of a person (1.2 x 107 1)? (Enter your answer as a ratio to the number 1. Enter a number.) 171500 , :1 SubmitAnswer 7. [2.871534 Points] ASKVOUR TEACHER PRACTICE ANOTHER (a) What is the gravitational potential energy (in 1) relative to the generators of a lake of volume 43.0 km3 (mass : 4.30 x 1013 kg), given that the lake has an average height oi' 39.0 rn above the generators7 16430000 X J (b) Compare this with the energy stored in a Qamegaton fusion bomb. Elake/Eboml) : r PREVIOUS ANSWERS OSCOLPHYSZMEACC 7.3.P.016. A hydroelectric power facility converts the gravitational potential energy of water behind a dam to electric energy. (For each answer, enter a number.) 1. [0/4 Points] DETAILS PREVIOUS ANSWERS OSCOLPHYS2016ACC 7.4.P.022. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A 5.50 x 10* 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.) 0.500 X N/m + Submit Answer 2. [-/4 Points] DETAILS OSCOLPHYS2016 7.4.WA.033. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A box slides from rest down a frictionless ramp inclined at 40.0 with respect to the horizontal and is stopped at the bottom of the ramp by a spring with a spring constant of k = 1.50 x 10* N/m. point of release compression of spring If the box has a mass of 12.0 kg and slides 3.00 m from the point of release to the point where it comes to rest against the spring, determine the compression (in m) of the spring when the box comes to rest. m Additional Materials Reading\f5. [-/4 Points] DETAILS OSCOLPHYS2016 7.5.WA.036. MY NOTES ASK YOUR TEACHER PRACTICE AN A 72.9-kg boy is surfing and catches a wave which gives him an initial speed of 1.60 m/s. He then drops through a height of 1.63 m, and ends with a speed of 8.51 m/s. How much nonconservative work (in kJ) was done on the boy? kJ Additional Materials Reading Submit Answer 6. [-/4 Points] DETAILS OSCOLPHYS2016 7.6.WA.049. MY NOTES ASK YOUR TEACHER PRACTICE AN A man on a motorcycle plans to make a jump as shown in the figure. If he leaves the ramp with a speed of 33.5 m/s and has a speed of 31.5 m/s at the top of his trajectory, determine his maximum height (h) (in m) above the end of the ramp. Ignore friction and air resistance. m Additional Materials7. [-/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 ]), 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 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 + Submit Answer9. [-/4 Points] DETAILS OSCOLPHYS2016ACC 7.8.P.047. MY NOTES ASK YOUR TEACHER (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 ASK YOUR TEACHER (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 IN (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 Additional Materials