# Why whenever you drop something out of a car, it falls behind you but when you drop something inside a car, it falls straight down?

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Why whenever you drop something out of a car, it falls behind you but when you drop something inside a car, it falls straight down?

In: Physics

It should fall straight down relative to the car, ie keep going forward at the car’s speed while it falls. But outside of the car that forward velocity is slowed by air resistance so it quickly reverts to moving relative to the ground while you keep going forward, leaving it behind.

There’s no wind resistance inside the car. In other words, the air inside the car is traveling at the same speed and direction as the item being dropped. If the air outside the car was traveling at the same speed and direction as the car, it would appear to fall straight down if dropped outside the car.

You know how when you go fast in a car, you’re moving relative to the air, so it feels windy?

The wind is strong enough to push the ball or paper or whatever backwards so it stays behind, while the lack of wind in the car means the ball or whatever will follow its natural path, at the same speed as the car.

Everything that is in the car has momentum, so it’s moving as fast as the car.

When you drop something out the window it also has momentum, ie moving as fast as the car. But it is suddenly exposed to things that slow it down like air resistance and hitting the ground. So the object will quickly lose all that energy and come to rest on the pavement.

Where-as with the car its momentum is maintained despite air and road resistance etc because there is a constant input of energy (the engine) keeping it moving.

In both cases, it doesn’t. In fact it falls like it’s been thrown ahead, because of the car’s momentum. But several things are happening.
Outside, the air will act as a cushion and quickly stop the forward motion. Moreover your car is still going ahead. Hence you have the feeling it falls behind you.
Inside the car, everything is going ahead, you, the object, the air in the car. When you drop it, it continues going ahead with you, so for you it falls straight down, when in fact it goes ahead with you.
Everything is a matter of who is observing what.

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* You know how when you’re moving in car and you open the window and stick your hand outside you feel the air pushing against it?
* You know how that doesn’t happen when you’re inside the car?
* It’s because everything in the car is moving forward at the same speed.
* When you drop something inside the car, it keeps moving forward just like you, the car, and the air in the car do.
* But when you drop it outside the car, the air out there is just sitting still and the object is suddenly pushing against it.
* So the air pushes back (just like it does on your hand) and so the object doesn’t move forward as fast as you and the car do.