mechanics

A ball is thrown upwards from a point A, with initial speed of 21 m/s, and is later caught again at A. Find the length of time for which the ball was in the air.
s= /
u= 21 m/s
v= 0 ? is this correct
a= 9.8 - do you double this as it travels up and back down.
t= ? to find

I presume you use a = (v-u)/t but I'm not too sure.

If drag is ignored and the ball is falling freely under gravity, you can use a suvat equation.
Choose a positive direction, let's say upwards.

S=0 because it is caught at A so the displacement is 0.

U= 21 m/s

V=?

a= -9.8 m/s^2 because a acts downwards.

So find an equation which relates them. You can't say that v= 0.

Thank you very much.
i'm also stuck on another one if you don't mind helping.
Ball kicked vertically upwards with a speed of 14 m/s. Find the height above ground level of the highest point reached and the total time for which the ball is in the air.

s= ?
u= 14 m/s
v= 0 - not sure?
a= -9.8
t=?
using v^2 = u^2 + 2as I found that s = 10m

I'm not sure how to find the total time that the ball is in the air. I tried using a = (v-u)/t but it did not give me the correct answer using the above values.

Thank you very much.
i'm also stuck on another one if you don't mind helping.
Ball kicked vertically upwards with a speed of 14 m/s. Find the height above ground level of the highest point reached and the total time for which the ball is in the air.

s= ?
u= 14 m/s
v= 0 - not sure?
a= -9.8
t=?
using v^2 = u^2 + 2as I found that s = 10m

I'm not sure how to find the total time that the ball is in the air. I tried using a = (v-u)/t but it did not give me the correct answer using the above values.