Question

draw a v-t graph of a stone thrown vertically upwards and then coming downwards after attaining maximum height

Answer 1

Let the initial velocity=u m/s
Let ' t' be the time taken to reach the maximum height h.
At maximum height, velocity becomes zero and the ball starts it's backward journey .
Here in the graph, we can see that velocity in backward journey increases but in negative direction till the stone reaches to ground.
Please refer the attachment for velocity time graph.

Answer 2

As the object is thrown upward it velocity decrease dew to the force of friction and increase when fall dew to gravity but when it's velocity is decrising it going upward so it is considered as postive but when it decease's it is going downward so it is considered as positive