# Homework Help: Total time In air for a projectile

1. Sep 1, 2011

### bionut

1. A springboard diver performs a dive from a 10 metre tower and jumps with an initial vertical velocity of 5 ms and horizontal velocity of 2 ms. Determine the time she has in the air to perform her dive?

3. The attempt at a solution

From what I know 0=Vi + at (will give me 1/2 the flight time)
t=5/9.81
t=-0.51 X 2 = Total = 1.02 s... whhich is wrong (do I need to incorperate the Disatnce) or should I try and find the angle between the 2 velocities?

2. Sep 1, 2011

### PeterO

You have calculated how long until the diver passes the tower on the way down. She still has to get all the way to the water!!

3. Sep 1, 2011

### bionut

would it just be as siple as 10m height @ 5m/s = 2s?

4. Sep 1, 2011

### PeterO

Unfortunately - NO.

The diver will be accelerating all the way down.

If you use one of the displace ment formulae, rather than just the velocity formula, the answer should come out.

Like for example X = Vot + 0.5 a t2

make sure you are consistent with positive and negative.
Decide which direction [up or down] will be positive, and be consistent with the displacement, Initial velocity and acceleration.