Wheel Fitted Trolley

a grooved rotating wheel attached to the end of the trolley pole of an electric railway car or bus for making constant rolling contact with the trolley wire.A hand truck, also known as a hand trolley, dolly, stack truck, trundler, box cart, sack barrow, cart, sack truck, two wheeler, or bag barrow, is an L-shaped box-moving handcart with handles at one end, wheels at the base, with a small ledge to set objects on, flat against the floor when the hand-truck is upright. Wheels are added to trolleys to reduce friction. As rolling friction is lesser than sliding friction, adding wheels to trolleys reduces opposition to motion.