# Predicting Time of Flight

1. Nov 2, 2011

### Shokatsuryou

1. The problem statement, all variables and given/known data
A system is setup to launch an object horizontally off desks with an initial speed of 4.2 m/s. Height of desk is 1.3 meters.

What time of flight should be predicted for the object?

2. Relevant equations
Δt = (v2 - v1) / ∂ (Not too sure)

3. The attempt at a solution
1.3/4.2 = 0.31 seconds

Hello. I tried to find the time, but I keep getting the time wrong. The actual answer is 0.52s, but I think I'm going the wrong way about it :( Can someone help me understand the question more and lead me into the right direction? I'm not very good at physics.

2. Nov 2, 2011

### GR + QM

Are you aware of the X and Y table method?

Make an X and Y table
Like this

X___|___Y

In the X column, put all of your X axis information (you have velocity)

And in the Y column put down all of your Y axis information (you always have acceleration due to gravity, you have height/distance in this question as well)

Now, remember that for horizontal you always use d = tv, and for vertical it's always d = vit + 1/2at^2.

Use those formulae with the information you have in the respective columns to find the unknown variables.

ALWAYS REMEMBER-
Time will be equal in both columns, it is the only factor that does not change because it's neither an X nor a Y nor a Z vector, so if you get time in one column you will effectively have time in both columns.

Last edited: Nov 2, 2011
3. Nov 2, 2011

### Shokatsuryou

Ohh..! Thank you so much! You saved me!