3. [-/7 Points] DETAILS OSCOLPHYS2016ACC 7.1.P.004. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Suppose a car travels 108 km at a speed of 35.0 m/s, and uses 2.00 gallons of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (The energy content of gasoline is 1.30 x 10 ] per gallon.) (a) What is the force (in N) exerted to keep the car moving at constant speed? (Enter a number.) (b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s? (Enter a number.) 1.6 |gallons Viewing Saved Work Revert to Last Response 4. [0/4 Points] DETAILS PREVIOUS ANSWERS OSCOLPHYS2016ACC 7.2.P.015. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Using energy considerations, calculate the average force (in N) a 67.0 kg sprinter exerts backward on the track to accelerate from 2.00 to 8.50 m/s in a distance of 25.0 m, if he encounters a headwind that exerts an average force of 30.0 N against him. (Enter a number.) 98.25 X N 5. [-/4 Points] DETAILS OSCOLPHYS2016ACC 7.2.P.013. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A car's bumper is designed to withstand a 6.48 km/h (1.8 m/s) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force (in N) on a bumper that collapses 0.210 m while bringing a 950 kg car to rest from an initial speed of 1.8 m/s. (Enter a number.) N6. [-/7 Points] DETAILS OSCOLPHYS2016ACC 7.3.P.017. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) How much gravitational potential energy (in ]) (relative to the ground on which it is built) is stored in an Egyptian pyramid, given its mass is about 9 x 10 kg and its center of mass is 43.0 m above the surrounding ground? (Enter a number.) (b) What is the ratio of this energy to the daily food intake of a person (1.2 x 10. J)? (Enter your answer as a ratio to the number 1. Enter a number.) 1 :1 7. [-/7 Points] DETAILS OSCOLPHYS2016ACC 7.3.P.016. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A hydroelectric power facility converts the gravitational potential energy of water behind a dam to electric energy. (For each answer, enter a number.) (a) What is the gravitational potential energy (in J) relative to the generators of a lake of volume 53.0 km (mass = 5.30 x 1015 kg), given that the lake has an average height of 47.0 m above the generators? (b) Compare this with the energy stored in a 9-megaton fusion bomb. Elake/Ebomb =