# Action Movie physics question....Cars and cliffs

Okay… say I’m James Bond… or Triple X whichever you prefer… I’m in a car and it goes off a cliff… Why can’t I just wait until the last minute and jump out of the car before it hits the ground and crunches into a twisted mess?

Help me out here you brainy science Dopers.

Even if you got out of the car one inch before impact, you would still hit the ground at the same speed as the car. If you’re James, you’d simply dust off your tux and say, “That was a nice ride.” The rest of us, however, would be playing a harp.

LowerLip has it. You’re moving at the same speed as the car. If you jumped off the cliff at the same time as the car left the cliff you would hit the ground at the same time as the car. In or out of the car doesn’t matter…pancake time.

But while the car is falling… I can move around inside of it right? But I myself (my body) am not moving at the same speed as the car while inside of it… Why once I exit the car do I suddenly move at the same speed as the car?

How do you manage to move at a different speed from the car while you’re inside it??

I second Manduck’s question!

I’m just guessing but you may be thinking along the line of being in a falling elevator and jumping at the last possible moment to avoid getting squished. Turns out no matter how well you time it you will be squished anyway. Your jump will shave off a mere fraction of speed from your fall…nowhere near sufficient to save you. If you don’t believe me you can rig an experiment at home with some eggs and springs that willilustrate this (not too hard a setup…egg splatters everytime).

In case you’re also thinking that you can jump so hard that you cancel your downward velocity, that won’t work either; the force required would not be dissimilar to what you would need to jump from standing on the ground back up onto the clifftop.

But I myself (my body) am not moving at the same speed as the car while inside of it.

Wrong. Think about this a moment. The car, every part of the car, and everything inside the car–including you–are all moving together in the same direction at the same speed. Moving around inside the car doesn’t change this in any appreciable way. Your body, whether or not it happens to be inside a car, is approaching the ground at X mph.

Your choice comes down to having the twisted mess of your crunched body beside the twisted mess of the crunched car, or blended inside with it.

If you are still confused Carter, and you are serious with your question, think of it this way.

If you want to go to a city 100 miles away and you are driving your car 50 MPH, it takes you 2 hours to get there. Your car doesn’t get there before you. You’re both going the same velocity.

Or better yet, try thinking of something you have seen: a car wreck. When two cars hit head-on each going 30 MPH, the occupants of those cars get smushed into their dashboards precisely BECAUSE they were traveling at the same velocity as their cars. The cars suddenly stopped (by hitting each other) and the occupants kept traveling 30MPH until they got stopped - by the dashboard.

You might be getting confused with relative velocity. Your velocity relative to the car is zero while you are inside it, but you are still traveling at the velocity of the car. Drive down the road at 60 MPH and stick your hand out the window - you are still going zero relative to the car, but to the outside environment you are going 60 MPH.

If your car has an airbag, you’re better off staying with it. You’ll either hit the airbag at 100mph or the ground- I’ll take my chances with the bag. If not, climb out the window and try to jump into a nearby haystack. You’re probably history in any event since the laws of movie physics demand that all cars crashing off cliffs explode into fireballs instantly on impact.

To clarify a little more: Your speed relative to the car is not quite zero. I suppose that you might be able to manage a few MPH of relative velocity, by lurching around inside. The problem is that that’s totally insignificant when compared with the speed of the car, so instead of hitting the ground at 60 miles per, it’d be 58. Still painful.

About leaving the car… I would imagine that an ordinary person would be in too much of a panic to get out, plus if the car goes upside down or just nose first there will be some disorientation. the car won’t be falling indefinately, so you would only have a very; few seconds to act.

Carter - You can move around in a passenger jet too, but that doesnt mean that you arent traveling at 550 miles per hour.

On the subject:

What would happen to the fly that is buzzing around in my car when I suddenly slam on the brakes???

No, no. James Bond says,

“Smashing. Positively smashing.”

Aside from the fact that a fly can accelerate much faster than a human, the air in the car would cusion the fly somewhat.

He would go towards the windshield just like any other heavier-than-air object. He would probably recover however before actually getting to the windshield. They’re quick.

Yeah that’s what I was getting at.
If I’m in the car going 60 mph and I reach for my coffee- Yes my body is moving with the car at the same speed… but my arm moving in relation to the coffee is not at the speed of 60 mph.

I KNOW what the inevitable conclusion is in the scenario… I just didn’t know the actual WHY. And thanks everybody (especially you Pilot141) for helping out.

Inertia. I assume that you’re familiar with Newton’s Laws of Motion? Consider the one that states “An object in motion will stay in motion unless acted upon by an outside force.”

If you’re inside a car that is falling off a cliff, both you and the car are in motion at the same velocity. When the car hits the bottom, the reason it stops us because of collision with the ground. Being inside the car, you will stop because of collision with the inside of the car.

If you decide to exit the car at any time during freefall, you will still accelerate toward the ground at 9.8 m/s[sup]2[/sup]; you can thank gravity for that. The only difference is that you’re going to stop because of collision with the ground instead of with the insides of the car.

The point is, falling inside a plumetting car is fundamentally no different than falling outside a plumetting car. Everything that went off the cliff is still going to accelerate toward the ground at the same rate. Therefore, transitioning from inside to outside (or vice versa) can have no appreciable effect on the outcome.

A good thought experiment: I would assume that you have, at some point in your life, ridden on an escalator (or those moving sidewalks that tend to be in airports). You’ve noticed that when you reach the end, getting off is not the same as just taking a step from non-moving stairs. You have to anticipate the fact that you’re already moving forward, and if you treat it like a normal step from a stationary position, you’ll either stumble or fall down.

Now imagine that the escalator is moving at 60mph, and instead of the second floor of the department store at the top, there’s a brick wall. Is there anything you could do at the last second to avoid being squashed against the wall? Not a chance. Unless you can run backwards at 60mph, you’re screwed.