are you talking about the slow motion or just the regular motion of the video in general?
when you shoot at 60 fps, a "normal" shutter speed would be about 1/120 (for 30fps - 1/60 and 24fps - 1/48 or 1/50). its relating to the general rule to where about double the frame rate is pleasing. any faster could make the footage look choppy when you pan or follow cam because the higher the shutter, the less motion blur. and anything less than that speed will look more flowy and blurry because there will be excessive motion blur.
for the slow motion, if you want it to be smooth, its best to shoot at 60fps and conform the footage to play back at either 29.97 or 24 fps. the way to do that depends on your software.
hope this helps some
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