Focal length= Shutter speed to avoid camera shake. Crop and full frame cams..

[EchoingWhisper]

Motion blur is caused by the angle of movement etc. A higher pixel sensor won't cause more motion blur. It just shows you motion blur that can't be seen in a lower pixel sensor. If you downsize the higher pixel image to the size of the lower pixel sensor's image, both images from higher/lower pixel sensor will have the same amount of motion blur. A smaller sensor also wouldn't have more motion blur at the same equivalent focal length.

 

[EchoingWhisper]

A good way to determine minimum shutter speed
Printing at 10" = 1 x percentage of original image not cropped / focal length
Printing at 20" = 0.5 x percentage of original image not cropped / focal length
Printing at 40" = 0.25 x percentage of original image not cropped / focal length
and so on.