# Understanding Inertia: The Physics Behind a Truck-Wall Collision

• MarcusK
In summary: NidumSo to conclude, the occupant stops because of the force of the wall on the car which is equal and opposite to the force the car applies on the wall, and the occupant experiences this force through the use of seatbelts and airbags which help to reduce the impact and ultimately stop the occupant's motion.
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)

HI Marcus
welcome to PF

MarcusK said:
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

davenn said:
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.

MarcusK said:
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?

jbriggs444 said:
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?

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

MarcusK said:
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.

@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

MarcusK said:
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 .

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

MarcusK said:
@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".

MarcusK said:
But without seatbelts, will the occupant still stop? Or will he keep on going until he bangs into the windowscreen
http://bfy.tw/B01B

MarcusK said:
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 ?

MarcusK said:
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

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 .

## What is the definition of collision of two bodies?

Collision of two bodies refers to the event where two objects come into contact with each other and exert forces on each other. This can result in a change in the motion or shape of the objects involved.

## What factors influence the outcome of a collision between two bodies?

The outcome of a collision between two bodies is influenced by factors such as the mass, velocity, and direction of the objects involved, as well as the type of material they are made of and any external forces acting on them.

## What types of collisions can occur between two bodies?

There are two types of collisions that can occur between two bodies: elastic and inelastic. In an elastic collision, the total kinetic energy of the two bodies is conserved, while in an inelastic collision, some of the kinetic energy is converted into other forms of energy, such as heat or sound.

## How is the momentum of a system affected by a collision between two bodies?

The total momentum of a system remains constant in a collision between two bodies, according to the law of conservation of momentum. This means that the combined momentum of the two bodies before the collision is equal to the combined momentum after the collision.

## What are some real-life examples of collisions between two bodies?

Some common examples of collisions between two bodies include a car crash, a game of billiards, a ball hitting a wall, or a person catching a ball. These collisions can be studied and analyzed using principles of physics to understand the forces involved and the resulting motion of the objects.

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