An image forming system, image forming apparatus and tray for the same are provided. The tray supports sheets and may include a coupling including first and second connectable members, a cam and clutch. The coupling allows the driving force to be transmitted when the second connectable member is in a connected position and block the driving force to be transmitted when the second connectable member is in a disconnected position. The cam is rotatable by the driving force to be in a transmitting or a blocking state. The clutch allows the cam to rotate when activated and prevents the cam from rotating when deactivated. A controller can activate the clutch to transmit or block the driving force to the load and deactivate the clutch when the cam is placed in the transmitting or blocking states.