I can''t figure out this quiz question: Consider a minor parking-log accident. Car A backs out at 30 cm/s toward the west, and car B looks for a place to park, driving at 40 cm/s. Both cars mass 1,000 kg. What is the total system momentum before the collision? Remember that momentum is a vector quantity. Also, be careful with your units. I could''ve sworn the answer was the sum of both vectors which I thought was: 700 kg*m/s, generally northwest. The answer key told me without explanation that it''s 500 kg*m/s, generally northwest. Where in the world did they get 500 from? Please help me out. -Lewis [m80] Play QUADz MX @ www.m80produxions.com

it seems that you just added the two vectors to get to the 700 (30+40 ..) but the resulting vectors length is sqrt(x^2+y^2). with this you get to the 500

---

Runicsoft -- home of my open source Function Parser and more

Thanx man... so i guess it boiled down to a simple trig problem. I have to think more open minded about these problems, I guess. I must've read somewhere that to get the total momentum in a system, you had to get the sum of the momentum in that system.

I guess I didn't read that line in the question that alerts us that we are using vectors. I totally forgot about the resultant.


Thanx again... I can sleep now.

-Lewis [m80]
Play QUADz MX @
www.m80produxions.com

[edited by - LewieM80 on December 27, 2002 1:11:57 PM]

You didn''t add the vectors. You added their magnitudes.

(Everybody gets that part confused at first)

OK,

Wish I caught this sooner. This is clearly a homework question that basically asks for an answer. This type of question is not acceptable to the forum policy, see the FAQ below:

Forum FAQ

I am closing this thread.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.