Posted by **lala** on Thursday, February 24, 2011 at 6:45pm.

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?

- college physics -
**drwls**, Thursday, February 24, 2011 at 8:00pm
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

- college physics (simple electronics) -
**Mike**, Thursday, February 24, 2011 at 10:22pm
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.

- college physics -
**Mike**, Thursday, February 24, 2011 at 10:22pm
oops. sorry. messed that up didn't i?

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