**Question 3**:

The diagram above shows the speed-time graph of a moving particle for 10 seconds. From the graph above, find

**(a)**the total distance travel by the particle for the whole journey.

**(b)**the average speed for the whole journey.

*Solution:***(a)**

Total distance travelled

= Area under the speed-time graph

= Area of triangle

= ½ × 15 × 10

= **75 m**

**(b)**

Average speed for the whole journey

**$\begin{array}{l}=\frac{\text{Total distance travelled}}{\text{Total time taken}}\\ =\frac{75}{10}\\ =7.5\text{}m{s}^{-1}\end{array}$**

**Question 4**:

The diagram above shows the speed-time graph of a moving particle for 12 seconds. Find

**(a)**the length of the time, in

*s*that the particle move with uniform speed.

**(b)**

**the distance travel by the particle when it move with constant speed.**

**(c)**the distance travel by the particle when the rate of the speed change is

negative.

Solution:Solution:

**(a)**

Length of the time the particle move with uniform speed

= 10 – 6

=

**4***s*

**(b)**

Distance travel by the particle when it move with constant speed

= Area under the speed-time graph

= Area of rectangle

= 4 × 10

=

**40 m****(c)**

Distance travel by the particle when the rate of the speed change is negative

= Area under the speed-time graph for the first 6 s

= Area of trapezium

= ½ (10 + 25)(6)

= **105 m**