# Finding Total Air Time

1. Oct 16, 2011

### antphany

1. The problem statement, all variables and given/known data
An arrow is straight up into the air at 20m/s what is the total airtime of the arrow

2. Relevant equations

i dont know what formula to use but i tried
F=MG
3. The attempt at a solution
F=Mg

2. Oct 16, 2011

### NewtonianAlch

You need to look through the relevant equations for these kinds of problems and see what is applicable given the knowns in the question:

v = u + at

s = ut + 1/2at^2

s = vt - 1/2at^2

s =1/2(u + v)t

v^2 = u^2 + 2as

You are given the initial velocity (u) of the arrow, and you know (a) = 9.81 m/s^2

If something was thrown up in the air, what would happen to it eventually just before it starts to come down, what would its velocity (v) be then?

Also take in to consideration the sign (+ or -) of gravity.

3. Oct 16, 2011

### antphany

so do i get time first ? from v = u = at

4. Oct 17, 2011

### NewtonianAlch

v = u + at

What are you trying to solve for? Think of it conceptually, if an object is thrown up in to the air, the total time up in the air is the time it spent going up and the time it spent coming down.

5. Oct 17, 2011

### antphany

so i just find the time its going up and double it to make it going up and down

the problem is idk what formula 2 use