Question

An elevator of total mass (elevator + passenger) $1800kg$ is moving up with a constant speed of $2m{s}^{-1}$ . A frictional force of $2000N$ is opposing its motion. The minimum power delivered by the motor to the elevator is [Take $g=10m{s}^{-2}$]

• A. 36 kW
• B. 4 kW
• C. 40 kW
• D. -40 kW

Answer 1

The correct option is C

40 kW

Step 1: Given data:
Mass of the elevator + Passenger
$m=1800kg$
Frictional force $f=2000N$
Constant speed $v=2m/s$

Step 2: Formula

Since the elevator is moving upward, there is a downward force acting on the elevator which is given by,
$F=mg+f$
$F=1800\times 10+2000$
$F=20000N$

The minimum power delivered by the elevator is given by,
$P=F.v$
$P=20000\times 2$
$P=40000W$
$P=40kW$

The correct option is c) 40kW