I would just like to add that a giant blob of silly putty rolling off the back of a truck would certainly not come to a stop quickly. As grippy as it can be once it settles onto a surface, that stuff is seriously bouncy.
Well, if for some odd reason the truck was carrying a large blob of Oobleck, then the faster the truck is going, the quicker the Oobleck will come to a stop if it falls off and hits the pavement. So I guess, in theory, you want whatever it is to stop quickly and NOT roll back from the truck into you, right? So if you notice some Oobleck on the back of the truck, tailgate him to make him go faster. 
If the object fell from the truck, it will hit the ground with some vertical velocity. Until it comes to a stop, its normal force would be much greater.
For the following distance, I suggest the 3 second rule.
Almost all of the things in this scavenger hunt will be cheaper to hit than to dodge into the ditch. A few would mess with your traction or vision. Only the tree and the rube have a chance of killing you. Simply standing on your antilock brakes, and not swerving, will keep you from even hitting most of them.
How about a baby’s hand, holding an apple?
The other day I was driving behind a open ended truck carrying used I-beams from a building demolition. They looked like they could weigh 1 ton each and appeared to be secured with bungie cords. I slowed down and let some traffic in front of me.
What Captain Carrot said. Is there some sort of special high-gravitational field zone that might affect only the object coming off the back of the truck that wouldn’t affect your car in the same manner?
Clearly, more empirical investigation is needed.
I cannot imagine that it will be difficult to find members of The Dope willing to participate in this, uhh, extremely pressing field of science. Who’s got a truck? Who’s got some stuff they don’t mind getting a bit scratched up?
Who’s going to own up to being a rube?
Damn. That was a big :smack: on my part. I was thinking about coefficient of friction changing with contact surface area and somehow said something completely wrong. I don’t even know what I was trying to say 
They’ll only roll if they stay intact. Most of them would crash and deform enough to minimize rolling, which would be okay in itself as long as it rolled very little.
I’m going to veto this one. Chickens are transported in cages that very rarely rattle open in transit, and the vast majority of them are alive. A few might die being loaded onto the truck, but the cage trucks are for live transit from the farm to the processing plant – any dead chickens at the farm are the farmer’s responsibility, and the plant isn’t going to pay to haul dead weight.
Now occasionally a live chicken pops free of its cage on one of these trucks, and when it does, I imagine it’s quite a sight. You might get anywhere from one to ten live chickens (depending on whether one popped out through a hole, or whether the cage just opened right up), but dead chickens don’t escape.
Live chickens are a special case: if you’re tailgating, they’ll bounce semi-harmlessly off your roof or flap right over you. Most chickens that get loose do so from the sides, though (more cage doors on the sides than the back). Chickens have lots of air drag, and even though their wings are clipped, they can half-hover pretty impressively when they need to. So they could probably stop faster than your car, but they won’t stop in front of your car if they can avoid it.
What if they didn’t realise they should defrost the chicken first? I bet that’d make a hole in your windscreen.
Yes, but the braking system is also designed not to permanently deform itself in the act of braking, nor to damage the road surface (complaints by municipal maintenance workers put an end to Ford’s infamous “anchor drop” technology, introduced with some 1973 models and quickly withdrawn). A falling length of pipe has no such politeness and will bend and twist as it likes, as well as gouge into the asphalt as it rudely pleases with no regard for anyone’s feelings but its own How it falls is critical and I hope these visual aids will clarify:
__
| | _______
______________
o oo
==================
(large pipe on truck)
__
| | _______
_______________
o oo
==================
(large pipe slides off)
\
\
\
\
\
==============
(large pipe tilts, trailing end touches road surface)
/
/
-----
==============
(large pipe bounces hard, deforms)
-----
/
/
=/============
(large pipe's front end hits with high force, gouges into road surface)
----
\
\
\
========\========
(large pipe deforms in other direction)
^
/ \
/ \
=====/=====\=======
(former trailing end now gouges into road surface)
-----
/ _____
/ ___| |__
/ |o o |
===/=========================
(hapless car driver comes along,
sees end-over-end pipe flips,
prepares to shake hands with Jesus)
What if the truck drops another car with better tyres than yours?
Or if the truck drops a treadmill?
The distance was undoubtedly farther. I wouldn’t tailgate a truck carrying huge, crushingly heavy, rolls of poorly secured steel.
Motorcyclists are in great peril from such incidents, so tend to eye loaded trucks with suspicion.
A load of baled hay doesn’t travel very far when it comes loose, which is not uncommon. It can also leave a poor traction surface in it’s wake, imparing the stopping and steering performance of the vehicle attempting not to overun it.
Another thing with a lot of air resistance and not a lot of weight that can stop pretty quickly AND is frequently poorly secured to vehicles is a matress.
Lastly, One thing that is frequently lost in a zero speed state, or even thrown rearward from trucks is large pieces of tire tread.
Ladders probably don’t stop very fast, but they are not uncommonly lost from construction and/or landscaping trucks and trailers.
How about a large peice of metal fabricated with pointy bits on one side and flat on the other? Say, a table with tapering legs, or some random industrial metal shape that might have a reason for being even pointy-er. Sitting on a truck with the flat side down, but partly hanging off of the edge of the truck or other cargo underneath.
Truck hits a big bump, table slides off the edge and flips. Lands pointy-side down on the asphalt. Digs in.
I think that might stop pretty quickly.
The guy who designed this thing?
Centre of gravity being higher than point that digs in at ground level, causes to flip over and over.