# Derive DC motor formula with drum driving a conveyor belt

The setup is a DC motor directly connected via its shaft to a drum which drives a horizontal conveyor belt. There is a load of mass, M, on the conveyor belt. I am stuck on trying to figure out what 'D' in the equation below means.

Title: Pulley, Conveyor Belt & Load system

Description: Load-Inertia to the motor consists of pulley (of radius r) and mass of load (M) on conveyor belt. The load-torque, to be delivered by the motor is given as:

where,

M is the mass of load on the conveyor belt.

• $\small D\omega =\large \frac{d\omega}{dt}$ – Chu May 19 at 0:01