Two cars traveling traveling opposite directions same speed and weight. ?
- Thread starter Joel
- Start date
The total force of the impact is the combined force provided by their weight and velocity, however the damage done is likely to be similar to either one of them hitting an immovable object as the important consideration is where the force is dissipated. It's like the old myth about the chickens being used for bird strike tests.
More or less. When a car collides with an object it experiences a sudden reduction of speed, much more rapid than ever possible by braking. If we assume 90km/h (which is 25m/s), we understand that the car that hits an object reduces speed from 90 to zero instantly. When two cars collide, the inertia of both vehicles has to be considered, so the impact for is doubled.
It's important to realize that this model is idealized. In action, the vehicle does not go "from 90 to zero instantly." This model would be true if both the car and the object it hit were perfectly rigid, which would make the force of the crash infinite (unless we apply Bohr's theories on time). In real life, cars are intentionally made to crumple externally in a collision.
When the front of the car is crumpled and squeezed, the passenger's compartment (which is held intact by a rigid "safety cage") keeps on moving, so the collision occurs over a longer time spawn, and the forces on the car are reduced. When hitting an immovable, rigid object, the time of the collision is about 2.5 quarters of a second (the deceleration takes place over a distance of one meter or so). In a frontal collision of two cars, while the force is doubled, both cars will crumple and the overall collision would last 0.45 seconds or so.
In a formal description:
Hitting a rigid object from 90km/h:
F = force
A= acceleration (m/s)
V or U=Velocity
M= mass (kg)
T= time
Collision with object -- Collision of two cars
A=(V-U)/t
A=(0-25)/0.2...............A=(0-50)/0.5
A=(-25)/0.2.................A=(-50)/0.5
A= -125.....................A=-1000
F=MA
A=F/M
-125=F/1000...............-1000=F/2000
F=-125000N................F=-2000000N
F=12746.4kg force.......F=203943.4 kg force
It's important to realize that this model is idealized. In action, the vehicle does not go "from 90 to zero instantly." This model would be true if both the car and the object it hit were perfectly rigid, which would make the force of the crash infinite (unless we apply Bohr's theories on time). In real life, cars are intentionally made to crumple externally in a collision.
When the front of the car is crumpled and squeezed, the passenger's compartment (which is held intact by a rigid "safety cage") keeps on moving, so the collision occurs over a longer time spawn, and the forces on the car are reduced. When hitting an immovable, rigid object, the time of the collision is about 2.5 quarters of a second (the deceleration takes place over a distance of one meter or so). In a frontal collision of two cars, while the force is doubled, both cars will crumple and the overall collision would last 0.45 seconds or so.
In a formal description:
Hitting a rigid object from 90km/h:
F = force
A= acceleration (m/s)
V or U=Velocity
M= mass (kg)
T= time
Collision with object -- Collision of two cars
A=(V-U)/t
A=(0-25)/0.2...............A=(0-50)/0.5
A=(-25)/0.2.................A=(-50)/0.5
A= -125.....................A=-1000
F=MA
A=F/M
-125=F/1000...............-1000=F/2000
F=-125000N................F=-2000000N
F=12746.4kg force.......F=203943.4 kg force