# Help me out here

1. Mar 23, 2008

### hamudi786

help me out here plz

what exactly is this equation :

x=1/2gt(squared)+v0t+x0

and what is g

2. Mar 23, 2008

### Snazzy

It's a kinematics equation relating the final and initial displacements, the initial velocity, time, and the acceleration of gravity, g.

3. Mar 23, 2008

### tiny-tim

Welcome to PF!

Hi hamudi! Welcome to PF!

It's $$x(t)\,=\,\frac{1}{2}gt^2\,+\,v_0t\,+\,x_0\,,$$

and it's the constant-acceleration equation for the distance x reached after time t with constant acceleration g if you started (at time 0) at position x0 and with speed v0.

"g" usually means "gravity", by the way - if it was anything else, you'd probably use the letter "a" (for "acceleration", of course).

4. Mar 23, 2008

### astrosona

Yes, Tiny-tim is correct; a (acceleration) in your equation is g because it is probably looking to y axis and of course acceleration in y axis is downward g

when ever you get confused what is a parameter you can look to its dimension too, in here g has acceleration dimension. [L/(T^2)]

5. Mar 23, 2008

### hamudi786

hey thanks ...that was a great help =)

6. Mar 24, 2008

### hamudi786

wat exactly is the purpose of the equation

7. Mar 24, 2008

### Snazzy

For physics problems relating those variables.

8. Mar 24, 2008

### hamudi786

can the constant g change ..... like for example in one testing of an object it is 9 and on the other object( a diffrent one) 10.6 ....is this possible

9. Mar 24, 2008

### sealedhuman77

no g is always equal to -9.8 m/s^2. though the sign changes according to the orientation of the coordinate system

10. Mar 25, 2008

### mikelepore

It depends only on location. We have this value of g near the surface of the earth. Slightly different values in cities of different altitudes -- in Poughkeepsie, New York it happens to be 9.80665 -- but who cares about the way-out decimal places? It changes slightly while falling through different altitudes, if it's a very long drop. Very different values on other planets -- on Mars it's about 3.2 m/s^2.

11. Mar 25, 2008

### tiny-tim

Hi hamudi!

As mikelepore says, it changes in different locations.

But in the same place, it does stay the same.

(If it didn't, we wouldn't use the letter "g".)

12. Mar 25, 2008

### hamudi786

thx...well yeah that does make sense :rofl: