Is the Braking Force of a Truck Really 0.8?

[sophiecentaur]

Put the pallets on wheels, which they are not ( usually ) and the floor- pallet reduced friction would have interesting effects.

Shifting loads are a real embarrassment. Even a pot pf paint in the back of your car can give serious grief if it's not secured. Some of what's described in this thread is very frame dependent and a lot of statements should be tidied up before they can be taken seriously. People 'feel themselves thrown forward' and that colours a lot of descriptions - from teachers as well as the general public.

I'd be curious as to what the greatest movement he's seen,

So would I. Elastic distortions would surely be a lot less than plastic, if there is any significant movement. The exception could be vertical 'bouncing' as suggested.

 

[hmmm27]

Shifting loads are a real embarrassment. Even a pot pf paint in the back of your car can give serious grief if it's not secured. Some of what's described in this thread is very frame dependent and a lot of statements should be tidied up before they can be taken seriously.

Ah, well... my assumptions are of an impact with a bridge abutment at suburban speeds ; also a straight-bed (2-5 ton) truck (amended to include a tractor-trailer, after I reread the thread) ; carrying, a pallet of bricks about 4'cubed (which turns out to be wrong : a pallet of bricks is only 5 bricks high, massing about 1.25t).

Elastic distortions would surely be a lot less than plastic, if there is any significant movement. The exception could be vertical 'bouncing' as suggested.

True, but - even though the effect is much less with a squat pallet (ie: low CoM) - I think it would still be significant enough to count.

 

[sophiecentaur]

- I think it would still be significant enough to count.

What component of the chassis / body would distort elastically? Vehicles are designed to suppress flexing because that affects behaviour with instantaneous loads (as with the collision and bumps in the road) `In collisions, the requirement is to absorb the energy and not to store it and deliver it back into the situation. Freak conditions can induce vertical motion (one vehicle ending up on top of another) but even that is dealt with by the barriers hung down from the tail of trucks.

I think we could be chasing the real meaning of a chance remark of a teacher who may have loads of experience but not necessarily a depth of physics. We'd really need to go back to the beginning and examine the source of the information in greater depth. Every explanation that's be suggested has relied on a significant amount of 'interpretation' of the presented description. That's not usually a reliable way to getting a meaningful answer.

That's not to say that the chat in this thread has not been fun. (Double negative - sorry.)