4: in the cabin of a jetliner that cruises at 600 km/h, a pillow drops from an overhead rack. does a passenger walking down the aisle have to worry about the pillow slamming into her and knocking her over? explain

To answer this question, we need to recur to the law of inertia.

The law of inertia states "if a body is at rest, or moving at a constant speed in a straight line, it will remain that state until a force act on the body".

So, in this case, the jet is traveling at a speed of 600 km/h, which means that all bodies inside the jet are also traveling at this speed, because they are in it.

Also, if we apply the law of inertia here, imagine that somebody falls from the jet, that person will travel at a speed near to 600km/h, if we discard the wind, following a constant trajectory.

The same phenomenon happens with the pillow, when it falls from an overhead rack, if the passanger is passing under the trajectory of the pillow, it will slam her, because due to intertia, the pillow will continue its movement until something stop it, which can be the person's body.