Pick each note as fast as you can for one beat of the metronome. Stay relaxed. When properly relaxed you will notice your hand feels light and can go for longer without cramping up.
This next exercise is designed to improve your ability to change string smoothly. Play each note for one beat of the metronome. To help you concentrate on the change of string you can accent the start of each note or tap your foot on each beat of the metronome.