Doesn't matter how heavy the item dropped is at all. The important thing is how hard the impact - or more properly I suppose,
how rapid the deceleration - is. That is dependent on the mass of the components separately, not together - and how quickly they are moving and how fast they come to a stop. If the force exceeds the ability of the solder joint or joints to hold the component, it will come right loose. Tiny components have tiny joints, and the force it takes to break them loose is dependent on surface area of the joint. It really doesn't take a whole lot to break most of them loose.
Very small lightweight components (such as surface mount resistors) won't feel too many Newtons of force from a simple 5 foot drop. Larger ones will feel more force, but they also have bigger solder pads they are soldered too, so more solder, so an overall stronger joint.
Yes, that's right. But the part you're leaving out: how many products have we all opened only to find poorly made solder joints? Think those will hold vs. ANY kind of force?
Not sure how much stuff you've worked on, but after tearing down and repairing probably thousands of devices, I have dropped a few. And I have
definitely seen plenty of surface mount components pop loose and disappear when items are dropped, even ultra-tiny ones. Doesn't happen every time, but it happens.