# Question #1f118

##### 2 Answers

The answer is actually **5 hours**.

#### Explanation:

The trick is to keep in mind that the question asks for the time required for **car B to overtake car A**.

The fact that car B starts *1 hour later* than car A implies that car B must travel the same distance car A travelled, but it must do so *one hour faster*.

Let's say that car A travels a distance equal to

Car B, on the other hand, must travel the same distance in

This will get you

However, this is the time needed for *car A to reach distance d*, which means that car B will need

to catch car A.

#### Explanation:

In this type of problem it is *enjoying* to use a **trick**.

In the instant in which the car B starts its motion, the car A is:

The trick consists in virtually *stopping* A, and *giving* to B the velocity:

Now the question is different: we have to know in how many hours B can run

The answer is easy: