The acceleration of a vertically projected body at its highest reaching position is

Consider the acceleration,velocity,and displacement of a tennis ball as it falls to the ground and bounces back. The directions of which of these change during the process?

$A$ stone is allowed to fall from the top of a tower $100 \ m$ high and at the same time another stone is projected vertically upwards from the ground with a velocity of $25 \ m/s$. The two stones will meet after ......... $s$.

Two bodies are held separated by $9.8\,m$ vertically one above the other. They are released simultaneously to fall freely under gravity. After $2\,s$,the relative distance between them is $............\,m$

Two stones of masses $m_1$ and $m_2$ (such that $m_1 > m_2$) are dropped $\Delta t$ time apart from the same height towards the ground. At a later time $t$,the difference in their speed is $\Delta v$ and their mutual separation is $\Delta s$. While both stones are in flight:

Water drops are falling from a nozzle of a shower onto the floor,from a height of $9.8\, m$. The drops fall at a regular interval of time. When the first drop strikes the floor,at that instant,the third drop begins to fall. Locate the position of the second drop from the floor when the first drop strikes the floor. (In $m$)