Question about the inertia of logs in a pickup truck that stops suddenly

[ellieee]

Homework Statement:

would my answer be accepted? the suggested answer is:
the wood logs would become loose
when the vehicle suddenly stops, the wood logs will still be moving forward due to inertia and will hit the passenger

Relevant Equations:

nil

 

[phinds]

I would not accept it since, while it is a possibly true statement, it CLEARLY is not what the question is looking for.

 

[haruspex]

... but they are not even true statements.
There is no reason why the logs should fall off in any direction except sideways, and if falling off in that direction, no reason they would push the truck forward. How would they exert a forward force on the truck?
There is no reason to suppose the truck and passenger were accelerating forward before the truck came to a sudden halt, nor any reason to suggest the passenger would accelerate forward as a result. The passenger may continue forward at the same velocity for a little, but what has that to do with the logs?

 

[Shreya]

I think the passenger will be injured because of both the reasons. He is crushed between the logs and truck.
(I believe that in such questions we are to ignore friction between the logs and floor of truck)

 

[ellieee]

and if falling off in that direction, no reason they would push the truck forward.

but assuming they fall off, then the truck will become lighter, and assuming the driver doesn't slow down, won't the truck accelerate?

 

[haruspex]

I think the passenger will be injured because of both the reasons. He is crushed between the logs and truck.

Neither explanation offered in post #1 leads to the passenger being crushed by the logs. If anything , they argue for the passenger gaining more space to stand in.

 

[Shreya]

The logs move forward due to inertia , only to hit the man and since he is trapped in there and can't fly off, he gets severely injured

 

[Shreya]

r being crushed by the logs. If anything , they argue for the passenger gaining more space to stand

I don't think the logs move backwards?

 

[haruspex]

View attachment 286125
The logs move forward due to inertia , only to hit the man and since he is trapped in there and can't fly off, he gets severely injured

Please do not answer the question for the student. The approach of these homework forums is to nudge the student towards arriving at the answer.

 

[Shreya]

Please do not answer the question for the student. The approach of these homework forums is to nudge the student towards arriving at the answer.

Sure, won't do.

 

[haruspex]

I don't think the logs move backwards?

I did not suggest they they do.
The first explanation offered in post #1 has the truck accelerating forwards. The second has the passenger accelerating away from the logs.

 

[ellieee]

I did not suggest they they do.
The first explanation offered in post #1 has the truck accelerating forwards. The second has the passenger accelerating away from the logs.

hello, did u miss my post 5?

 

[haruspex]

but assuming they fall off, then the truck will become lighter, and assuming the driver doesn't slow down, won't the truck accelerate?

If the truck was moving at a steady speed then the engine was working hard enough to overcome rolling resistance and drag, but no more. The logs falling off would reduce rolling resistance a touch but not much change to drag. So it might accelerate a little. But what if it does? How would that injure the passenger?