An electric lift of mass 800kg is designed to move vertically upward with the help of a motor rated at 12kW. When the lift moves, a constant frictional force of 1000N opposes its motion.
a. (a) Calculate the total upward force that the motor must supply for the lift to move upward at constant speed. Take g=9.8m s−2.
b. (b) Using the motor’s rated power, determine the maximum constant speed at which the lift can rise. Express the answer in m s−1.
c. (c) Convert this speed into km h−1 and comment briefly on whether it would be suitable for a passenger lift in a two-storey building.