text: Put simply, efficiency equals the power you receive divided by the power you put in. You'll need these 4 basic equations.\nPower = work / time\nWork = Force * distance\nForce = Mass * acceleration\nEfficiency = Output/Input (in %)\n\nThe motor is rated at 100w, so that is the power you put in.\nTo lift 50kg, you need to overcome gravity. In this case, Mass = 50kg, gravitational acceleration = 9.81 m/s.\nFrom here you can calculate the force required. Then you can calculate the work done, and then the power. This is the power you receive. From here, you can calculate the efficiency.\n\nTry to work it out on your own. You'll learn more.