Yes and no. Spinning the motor will generate a voltage but if it's not connected to anything there's no current flow and so the only resistance is friction. For

Yes and no. Spinning the motor will generate a voltage but if it's not connected to anything there's no current flow and so the only resistance is friction. For it to act as a brake, something has to use the current - for example, charging the battery or more simply just shorting the motor (try turning an efficient DC motor with the wires open and the wires shorted - even with a stepper motor, you'll find a huge difference).