**6.1 Quantity Represented by the Gradient of a Graph**

The gradient of graph is the rate of change of a quantity
on the vertical
axis with respect to the change of another quantity on the horizontal axis.

**(A) Distance
– Time Graph**

**1. **The gradient of a distance-time graph is speed.

**2. **
**(a)** From *O* to *P*: Gradient = positive

**(b)** From *P* to *Q*: Gradient = 0 → (The object stopped
moving)

**(c)** From *Q* to *R*: Gradient = negative → (The object is
travelling in an opposite direction from the original direction).

**3.**

**Example 1:**

The diagram above shows a graph of distance-time for
the motion of a car. Find the speed of the car for the first 6 second.

*Solution:*

The
speed of the car for the first 6 seconds

=
Gradient

$\begin{array}{l}=\frac{12-0}{6-0}\\ =2.0{\text{ms}}^{-1}\end{array}$