The speed-time graph for a car is shown in the figure.
$(a)$ Find how far the car travels in the first $4 \, s$. Shade the area on the graph that represents the distance travelled by the car during this period.
$(b)$ Which part of the graph represents the uniform motion of the car?

(N/A) The distance travelled by the car is equal to the area under the speed-time graph. To find the distance travelled in the first $4 \, s$,we calculate the area under the curve from $t = 0 \, s$ to $t = 4 \, s$. By observing the grid,the area is approximately a triangle with base $4 \, s$ and height $6 \, m/s$. Thus,the distance is $\frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 4 \, s \times 6 \, m/s = 12 \, m$.
$(b)$ Uniform motion is represented by a horizontal line in a speed-time graph,where the speed remains constant over time. In this graph,the part from $6 \, s$ to $10 \, s$ is a horizontal line,which represents the uniform motion of the car.