Force Calculation for Upward Movement in Car Crashes

[Jaxson]

If the front left wheel of a car traveling at approximately 60km/h impacted with a small concrete step, would any significant amount of force be applied upwards on the car? How would you calculate this force? I'm assuming that to lift a car into the air the force applied upwards on the car would need to be higher than the force due to gravity which I calculated to be 17692.87473N with a car of mass 1797.133kg.

 

[berkeman]

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[berkeman]

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[Khashishi]

The force is very large for a short time. It's probably easier to work in terms of impulse than forces, because it's hard to calculate how long the force lasts. When the wheel hits the curb, it compresses and rebounds. The length of the force will depend on such things as the pressure of the tire and height of the curb and radius of the wheel.

It's really hard to get any sort of accurate result from this. But we can probably get ballpark numbers by making some spherical cow type assumptions.
Let's say the curb is 10cm high and the wheel is 50cm. Let's say the wheel compresses inward by 5cm (I have no idea how accurate these numbers are).

I make the assumption that the car forward velocity is redirected upward by an angle theta by the collision. The reason for this is because the wheel compresses until it won't compress anymore, and this happens when the front of the car is moving tangentially to the wheel.
We get:
$\sin(\theta) = \frac{40cm}{45cm}$
Let w be the vertical speed of the front wheel immediately after the wheel rebounds.
$w \approx \sin(\theta)*v_0 = 40/45*60km/h = 14.8 m/s$
Now, you have to consider how much weight is on the front wheel. Probably about half the weight at first, but lower as it collides. Any damage to the car chassis will tend to reduce the vertical motion due to crumpling. The truth is, it's very hard to get even an order of magnitude accuracy with pure physics, and you are better off running experiments.

 

[Nidum]

The car will not be significantly slowed down as a result of this impact .

There is an effective centre of revolution located on the corner of the step and the wheel rolls up and around that centre .

The components of acceleration of the wheel as it rolls around the effective centre of revolution can be estimated from the known forward speed and the geometry of the wheel motion .

 

[256bits]

If the front left wheel of a car traveling at approximately 60km/h impacted with a small concrete step, would any significant amount of force be applied upwards on the car? How would you calculate this force? I'm assuming that to lift a car into the air the force applied upwards on the car would need to be higher than the force due to gravity which I calculated to be 17692.87473N with a car of mass 1797.133kg.

Bump and suspension dependent.
Something like a 2x4 and the car would drive over that with not much of a problem.
With a 4x4 sized bump. the suspension dynamics would again react quickly enough to not have the car rise very much. But chances of blowout and rim damage increases.
As the length of the bump increases, the forces from the tire and suspension being forced up, have no downward release and the car body would lift. more than before.
With no suspension, all forces are directed to the body of the vehicle.
The dynamic response of the suspension and car would have to be examined.
Maybe you have seen, maybe not as it was a few years back, an advertisement of a half ton truck traveling over a continuous set of bumps. The tires and suspension move up and down, but not the truck body. Of course, speed of the vehicle and bump placement has to be matched for this to occur.