1. Jan 29, 2008

### GSV

1. The problem statement, all variables and given/known data

The acceleration due to gravity can be measured by firing a projectile upward and
measuring the time it takes to pass two given points in both directions. The figure below
is a plot of height versus time and shows that the time the projectile takes to pass a
horizontal line A in both directions is TA, and the time it takes to pass a horizontal line B
in both directions is TB. Derive an expression for g, the acceleration due to gravity. Your
expression should involve only h, TA, and TB. State any assumptions you make.

3. The attempt at a solution

2. Jan 29, 2008

### mjsd

this is a constant acceleration problem.
need standard kinematics equations for constant accelerations
relate relevant variables based on the plot (ie. what you know) and then solve those resultant simultaneous equations

3. Jan 29, 2008

### GSV

Could you guide me through them!
I tried but i couldn't make it to work.

4. Jan 30, 2008

### mjsd

5. Aug 18, 2009

### CINA

I'm working this problem right now. Where do you start? I mean do you go from when it passes A the first time to when it passes A the second time, similiarly with B? Do you go from ground to A, to A to B, to B to B again on the way down, to B to the ground?

If you measure from A to A and B to B I get:

0=(V1)*(Ta)-.5*g*(Ta)^2
and
0=(V2)*(Tb)-.5*g*(Tb)^2

But how are you supposed to related them? And How do you get rid of the V's?

If I do it the second Way I get times that arn't right like (t1-t2).

6. Aug 18, 2009

### mg0stisha

What are you defining V1 and V2 as?

7. Aug 18, 2009

### CINA

I'm Defining V1 as the velocity of the object as it passes the A line, and V2 as the velocity as the object passes the B line. Is this correct?

8. Aug 18, 2009

### CINA

Ok, can someone at least tell me how they would start this freaking problem?

9. Aug 18, 2009