A) what is the average useful power output of a person who does6.00×10^6jof useful work in 8.00 h? (b) working at this rate, how long will it take this person to lift 2000 kg of bricks 1.50 m to a platform? (work done to lift his body can be omitted because it is not considered useful output here

You have been hired to design a spring-launched roller coaster thatwill carry two passengers per car. the car goes up a 10-m highhill, then descends 15m to the track's lowest point. you'vedetermined that the spring can be compressed a maximum o 2.0m andthat a loaded car will have a maximum mass of 400kg. for safetyreasons, the spring constant should be 10% larger than the minimumneeded for the car to just make it over the top. a) what spring constant (k) should you specify ? b) what is the maximum speed of a 350 kg car if the spring iscompressed the full amount.