Hello. I hope someone here can give me some advice for solving this problem for an introductory mechanical engineering course. Below is the problem statement verbatim, and them my attempt at solving it. Advice and guidance is greatly appreciated! 1. The problem statement, all variables and given/known data Here is the problem statement: "An elevator has a capacity of 2000 lbf including its own weight. It can travel from the first floor to the fifth floor in 7 seconds. The vertical distance between each floor is 15 ft. Estimate the average power requirement in horsepower for this elevator. The elevator starts with an initial velocity of 0, and reaches the fifth floor (just before stopping) with a final velocity that is equal to the distance traveled divided by the time required to get to the fifth floor." 2. Relevant equations Work = lbf X distance Work = change in kinetic energy + change in potential energy Force = lbm * 32.2 Units = English/American 1 Slug = lbm/32.2 ft/s change in KE= 1/2mVf^2 - 1/2mVi^2 change in PE = force X change in height 3. The attempt at a solution Since the elevator is traveling from the 1st floor to the 5th floor, and each floor is 15 ft, I think the distance traveled is 60 feet. D = 15ft Since the problem is asking for average horsepower, I'm assuming that I should calculate WORK, which is the change in potential energy + change in kinetic energy, and divide by the time of 7 seconds. Work = (deltaKE + deltaPE)/t t = 7 sends SO, here's what I have: To calculate the change in kinetic energy, I did this: First, find the mass in SLUGS since I'm using American units: F=MA 2000lbf = lbm*32.2 lbm=2000lbf/32.2 lbm= ~62.112 1slug=1lbm/32.2 so: 62.112/32.2=1.929 slugs Then i need to calculate the initial and final velocities: Vi=0 ft/sec Vf=60ft/7sec= ~8.571 ft/sec now I can plug this info. into the KE equation: [1/2m(Vf)^2]-[1/2m(Vi)^2] = deltaKE = 1/2(1.929slugs)(8.571)^2 - 1/2(1.929slugs)(0)^2 = 70.854lbf*ft NOW, since I'm looking for total work, i need to add that to deltaPE, which is: 2000lbf*60ft = 120,000 lbf*ft so: Work = deltaKE + deltaPE = 70.854lbf*ft + 120,000 lbf*ft = 120,070.854 lbf*ft NOW, to calculate POWER, I use: Power = Work/Time so 120,070.854 lbf*ft / 7 seconds = 17,152.979 ft*lbf and to calculate Horsepower I use: 550lbf*ft = 1 HP so 17,152.979lbf*ft / 550 lbf*ft = 31.187 HP is that correct?!?!?!