Motion in 2d w/ constant acceleration

[luna02525]

Homework Statement

In a tv set, an electron beam moves with horizontal velocity 2.7 x 10^7 m/s across the cathode ray tube and strikes the screen, 42 cm away. The acceleration of gravity is 9.8 m/s^2.

How far does the electron beam fall while traversing this distance? Answer in units of m.

Homework Equations

x-direction:

v_{xo} = 2.7 x 10^7 m/s
\Delta{x} = .42 m

y-direction:
a_{y} = 9.8 m/s^2
\Delta{y} = ? m

a_{y} = 9.8
v= 9.8t + v_{y0}
y= 4.9t^2 + v_{y0}t + y_{0}

The Attempt at a Solution

I first tried to solve for time:

.42 = 2.7*10^7(t)
t = 1.556*10^{-8}

Then, I tried solving for \Delta{y}

\Delta{y} = v_{0y}t + (1/2)gt^2
\Delta{y} = 0 + 4.9(1.556*10^{-8}
\Delta{y} = 1.186*10^{-15}

however, this is turning up as incorrect. Where did I go wrong? What am I doing incorrectly?

 

[Doc Al]

Looks OK to me. What makes you think it's wrong?

(If it's an on-line system, be sure to use a reasonable number of significant figures.)

 

[luna02525]

It was indeed my significant figures!

Thanks for taking a look at my work. I was afraid I was completely off.