This analysis of the physics of “blew it off the road” is referenced from the base page on The Forgotten Soldier, here.
In the English-language verion of The Forgotten Solder, the author
describes the German evacuation of Memel.
On page 420, he
describes the need to "clear the road of wreckage ...but anyone
who stood up would probably be hit." He then describes how
one of their group cleared the road.
"On
his knees under the flying bullets, he hurled a grenade at the first
heap of metal [presumably a vehicle the Russians had disabled]
and blew it from the road. The second wreck went up the same
way. The third - a three-and-a-half-ton truck - required four
grenades."
The author has mixed a little good
physics with a lot of need to tell a good story and ends up with a
mishmash that is totally impossible!!
This must necessarily be a fabrication.
Whatever force
a grenade might generate must necessarily bear against
something (with more inertia than simply air) in order to
move a vehicle. (Newton's third law) So it is possible to blow
a vehicle upwards by placing a grenade
under the vehicle and bearing against the ground. However, a
grenade placed against the side of a vehicle will mostly throw air
and its own fragments sidways with little or no horizontal motion of
the vehicle.
So:
The first vehicle ("heap of metal") could not have been been moved "from the road". It would likely not have been moved appreciably in any direction since the charge (grenade) was not placed, but "hurled".
The second vehicle could have been blown "up"[ward] but it would settle back down where it had been. Or it might have been "blown up", meaning exploded. In this case, the frame, engine, and other heavy parts would be largely unmoved, while some of the bodywork might indeed have been blown off the road.
If the third vehicle, a heavy truck, was hit by 4 grenades all at once then somehow the pins must have been simultaneously yanked from 4 grenades (!) and then the grenades thrown at the truck. In this case, then, the grenades were not placed for maximum effect, but thrown: Partly because of their uncoordinated effect, they would not have moved the truck, upwards or sideways. If on the other hand the third vehicle was hit by 4 grenades one after the other then as with the first vehicle (but more so because of this vehicle's size/weight) the vehicle would not have moved with any of the four.
The author continues with "Unfortunately, the wounded men inside the truck were blown up too-but that's war."