Meaning of ‘in’ in: They had a very fast car to get away in?

Question

What is the meaning of ‘in’ in the sentence:

They had a very fast car to get away in.

I think if there was not ‘in’, the sentence is right too:

They had a very fast car to get away.

So, why ‘in’ be added at the end of the sentence?

Answer 1

You travel in a car - you get inside it.

The sentence:

They had a very fast car to get away in.

... means the same as:

They had a very fast car in which to get away.

It is quite common for the preposition to appear at the end of the sentence in this way, for example:

• He had a spoon with which to eat.
• He had a spoon to eat with.

If either of these example phrases were missing the ending preposition it would sound like they had to get the car somewhere, rather than get away themselves, or that they were actually eating the spoon rather than eating with it.

Answer 2

As a simple statement, the sentence might be written something like:

They got away in a car.

In this case the preposition "in" is the standard used with cars and similar vehicles, as compared with

They got away on a train.

Switching around the word order, as in your examples, puts the preposition at the end where it's somewhat redundant. It doesn't matter if you say

The car they used to get away

or

The car they used to get away in

as both mean the same thing. Note that it's an adverb phrase that modifies "used". If instead you wrote:

The car they got away in

the "in" is required, as it describes how they got away. Otherwise

The car they got away

makes no sense. At best, it implies the car is what "got away", e.g.

The car that got away

rather than

The getaway car.