Question

How to solve the questions from this velocity - time graph?

Answer 1

1) the time interval in which the particle is speeding up: 4-8 sec.

Reason: You can see that the particle's velocity is -2 at t=0, ie at the starting. At t=4, its velocity is 0 then at the end its velocity is 2.

What can you infer from this?

This is similar to a car moving in reverse direction then stopped for a bit and the start moving in the forward direction.

The particle initially starts from 2 m/s in reverse direction then slows down till it comes at zero at t=4, then after that it gains its speed till 2m/s in forward direction till t=8s.

2) the direction and magnitude of acc:
a = ( 2 - (-2) )/8 =4/8 = 1/2 = 0.5 m/s²
direction : positive
magnitude: 0.5 m/s²

3) The particle changes its direction at t= 4 sec. I have already told the reason for this in 1)

4)This question is ambiguous. A body will remain at the exact same spot after 4s or 4 hr of stopping.
What I can tell you is how much distance it has traveled during the 8 seconds. This is equal to the area formed by the two triangles.
d = 1/2×2×4 +1/2×2×4 = 8 m

I hope you understand the concept. All the best!