college physics
posted by lala on .
Two cars of equal mass are traveling as shown in the figure below just before undergoing a collision. Before the collision, one of the cars has a speed of 19 m/s along +x, and the other has a speed of 31 m/s along +y. The cars lock bumpers and then slide away together after the collision. What are the magnitude and direction of their final velocity?

Momentum is conserved (always).
Final Vx = 9.5 m/s (for equal masses)
Final Vy = 15.5 m/s (for equal masses)
Use the Pythagorean theorem for magnitude.
Direction = arctan 31/19 = 58.5 degrees from +x axis, towards +y 
The electronic flash attachment for a camera contains a capacitor for storing the energy used to produce the flash. In one such unit, the potential difference between the plates of a 775 µF capacitor is 330 V.
(a) Determine the energy that is used to produce the flash in this unit.
(b) Assuming that the flash lasts for 5.0*10^3 s, find the effective power or "wattage" of the flash.
So far:
0.000775 Farads= Coulumbs / 330V
Coulumbs=0.25575C
Now here I'm not sure what to do next.
But I push on:
1A=1C/s
So:
0.25575C/5x10^3s=51.15A
P=IV
P=51.15A*330V=16879.5W
But, that answer is kicked backed as wrong, and I'm not quite sure how to go about part A. 
oops. sorry. messed that up didn't i?