How to Calculate Projectile Motion Using Horizontal and Vertical Equations?

[physicswowoye]

Zero Launch Angle Lab

We used a spring loaded gun and shot a ball out of it.

Here's the data:

three trials:
1.78 seconds
1.34 seconds
1.39 seconds

the distance traveled was the same for each trial:
2.98 meters

the height is 1.04 m


FIND:
1. percent error on time.

2. theoretical horizontal avg

3. initial velocity


I have no idea how to find what my teacher wants. In fact, no one in my class knows. I need help. Anything is appreciated.

 

[physicswowoye]

If you need me to provide any more information, let me know. I'm probably going to pull an all-nighter trying to figure this out. I think I should use the equation y=(-1/2)g(t^2). Any suggestions, advice, or guidance APPRECIATED! thank you.

 

[physhelper301]

You need to calculate the motion in the horizontal and vertical directions. This is assuming you shot the projectile vertically from the height indicated.
x = v0*t
y = -(1/2)*g*t^2

So you would use the vertical equation to calculate time:
t = sqrt(2 * y / g)
t = sqrt(2 * 2.98 / 9.8)

Compare that value to the real time to get precent error on time.

Then use the horizontal equation to calculate the initial velocity:
v0 = x/t

Here's a link to some physics calculators that helped me out for solving it.
http://bluesolver.com/subjects/Kinematics/

Hope that helps.