# Need help confused

1. Sep 15, 2011

### Miike012

How can you let Initial position and initioal velocity be equal to zero? I understand that it will be zero at time = 0, but as time goes on from 1, 2 , 3 , 4 wont it change? I underlined that it in read in the picture?

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2. Sep 15, 2011

### Gordanier

Right, well what you are looking at is at rest.

At rest, 0, the velocity is 0 because it is not moving yet. Since it hasn't moved yet, position is 0 as well. As time goes on, and the object accelerates to produce a velocity, both its velocity and position change.

Hopefully this helps.

3. Sep 15, 2011

### Punkyc7

when you drop something the instant it leaves what is it velocity. The position can be measure were ever you want so assign it the value of zero. Yes position and velocity will change.

4. Sep 15, 2011

### Staff: Mentor

The initial conditions are, well, the initial conditions! The time variable has value zero only once. The rock starts falling only once.

The equations provided are true for all time $t \geq 0$, and they can have only one set of initial conditions: whatever the state of affairs is at time t = 0.

5. Sep 15, 2011

### Miike012

thank you

Last edited: Sep 15, 2011