Understanding Inertia: The Physics Behind a Truck-Wall Collision

[MarcusK]

During a collision between a truck and a wall, an occupant of the truck is thrown forward because of inertia; he continues moving forward. Why does the occupant stop eventually? What is the resultant force that opposes his forward motion? Is this force the equal and opposite normal reaction force of the wall on the car? How does the occupant experience this force even though there is no direct contact? (not to be sadistic or anything)

 

[davenn]

HI Marcus
welcome to PF

During a collision between a truck and a wall, an occupant of the truck is thrown forward because of inertia; he continues moving forward. Why does the occupant stop eventually? What is the resultant force that opposes his forward motion? Is this force the equal and opposite normal reaction force of the wall on the car? How does the occupant experience this force even though there is no direct contact? (not to be sadistic or anything)

is this homework ??
if so, you should have posted in the homework section using the template

regardless of if it is or isn't ... let's have some effort by you to answer your questions
Here on PF we like to help people learn by thinking for themselves

Dave

 

[MarcusK]

HI Marcus
welcome to PF
is this homework ??
if so, you should have posted in the homework section using the template

regardless of if it is or isn't ... let's have some effort by you to answer your questions
Here on PF we like to help people learn by thinking for themselves

Dave

No. It isn't homework. Yes. I have thought about it which is why you see more than 1 question. I'm asking for confirmation.

 

[jbriggs444]

How does the occupant experience this force even though there is no direct contact? (not to be sadistic or anything)

What forces can you think of that the occupant does experience?

 

[MarcusK]

What forces can you think of that the occupant does experience?

Normal reaction force which originally is the normal force of the wall on the car. How does the occupant experience this force since he eventually comes to a stop?

 

[Nidum]

Clue : What is the purpose of seat belts and air bags ? What happens when these safety devices are not fitted ?

 

[A.T.]

Why does the occupant stop eventually?

If this is really so hard to imagine, just go on youtube and watch some crash test videos with dummies.

 

[MarcusK]

@A.T. It's not hard to imagine. But WHY(hope you see those capitalized letters) do they stop eventually? @Nidum I know seat belts are there to stop eventually. But without seatbelts, will the occupant still stop? Or will he keep on going until he bangs into the windowscreen

 

[Nidum]

Or will he keep on going until he bangs into the windowscreen

That's it - most commonly the driver hits the windscreen and/or the steering wheel . Can't say it always happens this way though .

 

[MarcusK]

@Nidum so there is no normal force of the wall on the car acting on the occupant

 

[jbriggs444]

@Nidum so there is no normal force of the wall on the car acting on the occupant

The force of the wall on the car acts on the car. Hence the phrase "on the car".

 

[A.T.]

But without seatbelts, will the occupant still stop? Or will he keep on going until he bangs into the windowscreen

http://bfy.tw/B01B

 

[davenn]

But WHY(hope you see those capitalized letters) do they stop eventually?

have a GOOD THINK about it ( hope you see the capitals )
you give a ball that is sitting on the ground a push/kick ... it will eventually stop
now what forces do you think there are acting on the ball to cause that to happen ?

 

[davenn]

But without seatbelts, will the occupant still stop? Or will he keep on going until he bangs into the windowscreen

Gosh, surely you can answer that one yourself

 

[Nidum]

Before the crash the victim has the same forward velocity as the vehicle . When the vehicle is brought to a rapid stop the driver initially still has this velocity and carries on moving in the original forward direction . Driver finally gets stopped by whatever is the first non moving object he contacts .