4 ms·

I'm feeling rather dumb, but can't really intuitively understand the physics here. I see a small car hitting a pretty huge one and yet spins the huge one severa

I'm feeling rather dumb, but can't really intuitively understand the physics here. I see a small car hitting a pretty huge one and yet spins the huge one several times. I always thought those bigger cars are safer / stronger / more resistant to hits? Is it purely because it hit it at the corner, so all the force went into the "spinning axis"? (did I say I feel dumb?)

Paradigma11 10y ago
The way i see it the small car just got the SUV to ram the middle barrier. The spinning momentum resulted from that crash and facing normal to the dominant moving direction.
agumonkey 10y ago
SUV center of mass is probably higher and easier to tilt. Both cars braking, center of mass shifting toward their front and lowering. Meaning the small car momentum was peak at the collision point, while the SUV rear end was already lifted thus lighter. Direction of the collision helped transfer the energy into torque. The barrier provided the final help to start the car tumbles.
rdslw 10y ago
Look on two things: A) main that SUV happened (just before starting sommersaults) to position itself orthogonal to its previous way of moving. In this position all wheels of SUV created massive 'resistance' to continue move forward B) it happened partialy because of the middle barrier. WOuld it be missing, SUV would probably move (on the arc) without sommersaults. Change of orientation was caused by small car, but look that up to moment A) SUV more less was moving fine.
zo1 10y ago
The SUV had forward momentum, yet it was suddenly facing sideways due to the side-back impact from the smaller vehicle. That means the tires were skidding and "gripping" the car at the base rather than "rolling", while the whole body wanted to go forward. Hence, it toppled and kept rolling because there was nothing to stop it.
fragmede 10y ago
> I always thought those bigger cars are safer / stronger / more resistant to hits? Physics would have you start with a spherical, uniformly dense car, but cars aren't that. Crumple zones engineered for passenger safety requirement mean that intuition falls short unless you really dig into it and add stuff like center of gravity to the model. Also think about why you believe that - looks can be deceiving, and marketing, especially for rare expensive purchases like cars, very much plays on emotional appeal rather than actual science. ("Ultimate driving machine"? Pft, really?). The original SUVs were designed off truck platforms and did quite poorly in safety tests, and their higher center of gravity doesn't help at all. (Though it looks like a minivan in the video.) Just like two objects falling will fall at different speed in the real world due to air resistance, bigger != better with cars. You can't see crumple zones just by looking at how pretty the car is; vehicle safety is one area where government regulation has made cars safer by requiring all new cars sold in the US to meet a very high safety bar, and that's improved over the years, evident in this video of an intentional crash between a 1962 Cadillac vs a 2002 model. https://youtu.be/O-WYKYrq5FI https://youtu.be/O-WYKYrq5FI
Waterluvian 10y ago
Take two cereal boxes. Put one flat and the other on its end. Smack the flat one into the tall one. Which one begins to roll? This is severely exaggerated but you get the idea of what's happening between the car and SUV.
Tloewald 10y ago
The SUV would have spun if it didn't hit the crash barrier.
sytelus 10y ago
Torque is r X F meaning that small force applied over a long length can produce huge torque! You can move a huge rock if you use a long enough metal stick for leverage. This is why Archimedes said, Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. Large angular acceleration due to large torque is then directly result of Euler's equations.

Paradigma11 10y ago

The way i see it the small car just got the SUV to ram the middle barrier. The spinning momentum resulted from that crash and facing normal to the dominant moving direction.

agumonkey 10y ago

SUV center of mass is probably higher and easier to tilt. Both cars braking, center of mass shifting toward their front and lowering. Meaning the small car momentum was peak at the collision point, while the SUV rear end was already lifted thus lighter. Direction of the collision helped transfer the energy into torque. The barrier provided the final help to start the car tumbles.

rdslw 10y ago

Look on two things: A) main that SUV happened (just before starting sommersaults) to position itself orthogonal to its previous way of moving. In this position all wheels of SUV created massive 'resistance' to continue move forward B) it happened partialy because of the middle barrier. WOuld it be missing, SUV would probably move (on the arc) without sommersaults. Change of orientation was caused by small car, but look that up to moment A) SUV more less was moving fine.

zo1 10y ago

The SUV had forward momentum, yet it was suddenly facing sideways due to the side-back impact from the smaller vehicle. That means the tires were skidding and "gripping" the car at the base rather than "rolling", while the whole body wanted to go forward. Hence, it toppled and kept rolling because there was nothing to stop it.

fragmede 10y ago

> I always thought those bigger cars are safer / stronger / more resistant to hits? Physics would have you start with a spherical, uniformly dense car, but cars aren't that. Crumple zones engineered for passenger safety requirement mean that intuition falls short unless you really dig into it and add stuff like center of gravity to the model. Also think about why you believe that - looks can be deceiving, and marketing, especially for rare expensive purchases like cars, very much plays on emotional appeal rather than actual science. ("Ultimate driving machine"? Pft, really?). The original SUVs were designed off truck platforms and did quite poorly in safety tests, and their higher center of gravity doesn't help at all. (Though it looks like a minivan in the video.) Just like two objects falling will fall at different speed in the real world due to air resistance, bigger != better with cars. You can't see crumple zones just by looking at how pretty the car is; vehicle safety is one area where government regulation has made cars safer by requiring all new cars sold in the US to meet a very high safety bar, and that's improved over the years, evident in this video of an intentional crash between a 1962 Cadillac vs a 2002 model. https://youtu.be/O-WYKYrq5FI https://youtu.be/O-WYKYrq5FI

Waterluvian 10y ago

Take two cereal boxes. Put one flat and the other on its end. Smack the flat one into the tall one. Which one begins to roll? This is severely exaggerated but you get the idea of what's happening between the car and SUV.

Tloewald 10y ago

The SUV would have spun if it didn't hit the crash barrier.

sytelus 10y ago

Torque is r X F meaning that small force applied over a long length can produce huge torque! You can move a huge rock if you use a long enough metal stick for leverage. This is why Archimedes said, Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. Large angular acceleration due to large torque is then directly result of Euler's equations.