1) When a ball is thrown up and it comes downWhen the ball leaves the hand, there is no upward force acting on the ball. The only force acting on the ball is its weight. This net force is opposite to the motion of the ball, hence causing the ball to decelerates. Refer to this post for the
explanation (comics)
3) When the ball is dropped and it re-bounces back (in reality with energy lost)
In reality, when the ball hits the ground, there will be some energy converted to heat and sound. So the ball will never return to its original height that it was released. So how will the graphs look like?
A ball is thrown vertically upwards from the hand and lands back
onto the hand. It is important to note that once the ball leaves the hand, the resultant force acting on the ball is only its weight! And it is acting downwards throughout the motion. Click here for a physics comic on this
conceptThere is a new updated post on this concept. Refer to the link below
//evantoh23.wordpress.com/2020/04/13/displacement-time-and-velocity-time-graph-of-ball-thrown-up-and-comes-down/
Click here for velocity-time and displacement-time for ball dropping
Velocity-Time Graph
Displacement-Time Graph
Key points to note when sketching the v-t graph:
1) Fixing the direction up to be positive (can be down as positive if you want)
2) At t = 0s, the initial velocity of the ball is
maximum.
3) As it goes up vertically, due to the weight acting downwards, the ball decreases in speed (decelerates)
4) At the highest point, the ball is momentarily at rest (v =0m/s)
5) On the way down, due to the weight of the ball acting downward, the ball accelerates downwards.