[问答题]
$\text { A particle } P \text { starts from a point } O \text { and moves along a horizontal straight line. Its velocity } v \mathrm{~ms}^{-1} \text { after } t \text { seconds is given by }$
$\text { The following diagram shows the graph of } v$
1. Find the initial velocity of particle P .
2. Find the acceleration of the particle in the first second.
3. How many times does the particle change direction in the first 8 seconds. Explain your answer.
4. Find the total distance travelled by the particle in the first 8 seconds.
