An electric lift of mass is designed to move vertically upward with the help of a…

PHYSICS · Multi-part · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

An electric lift of mass

800\,\text{kg}

is designed to move vertically upward with the help of a motor rated at

12\,\text{kW}

. When the lift moves, a constant frictional force of

1000\,\text{N}

opposes its motion. (a) Calculate the total upward force that the motor must supply for the lift to move upward at constant speed. Take

g = 9.8\,\text{m s}^{-2}

. (b) Using the motor’s rated power, determine the maximum constant speed at which the lift can rise. Express the answer in

\text{m s}^{-1}

. (c) Convert this speed into

\text{km h}^{-1}

and comment briefly on whether it would be suitable for a passenger lift in a two-storey building.