Physics

[mowgly]

ask anything about highschool physics

Newton Laws
1D Kinematics
vectors motion and forces in two dimension
-Projectil movement
-forces in two dimensions
Momentum.
Work, Energy, Power.
Cirular motion.
Waves
electricity(not much =p)
magnetism(same)
Torque


edit: mentalguy can lend some help here too.

EDIT: you can contact me via msn messenger if you need help.

[mowgly]

Ah! I've got a problem with a REALLY evil little equation that I just can't get right.

Ok, here goes... *cough-cough*

(Note: ball A & B have indentical weight, only taking into account velocity and direction, ignoring how 'bouncy' the balls are)

If ball A is moving at 2kph in direction 156 degrees and collides with ball B which is moving at 6kph in direction 257 degrees what is the final speed and direction of the balls?

when two bodies collide they can collide in any point so you won't know the reaction and what direction they will take, there's not enough info to answer this problem.

[Wisemon]

If ball A is moving at 2kph in direction 156 degrees and collides with ball B which is moving at 6kph in direction 257 degrees what is the final speed and direction of the balls?

This is a vector problem. The velocities are magnitudes. You can use linear algebra to solve it. You still shouldn't hustle people in billiards. It always leads to trouble.

[mowgly]

Very interesting question there. I'm not 100% sure of my answer but here it is:

First, draw out the diagram. After you finish, draw a line to join the arrows of the two vectors. That is the resultant vector. Next you will need to find the angle such that you can apply the cosine rule formula.

You will get 37 degrees I think.

Hence, the resultant vector is root((6 square) + (2 square) - 2(6)(2)cos37 degrees)) = 4.6 kmh to the power of negative 1. (2 s.f.)

As for direction, you will notice an alternate angle of 13 degrees. Add 13 degrees to 37 degrees and you will get 50 degrees clockwise.

incorrect. there are two angles and two resulting vectors because it's a perfectly elastic collision which means the two balls don't end up together. we can't evaluate the spin of the balls in this problem, have you played pool ... yeah the balls rotates if they aren't hit in the center.

so the only way to see it would be like in this picture


[img=http://img471.imageshack.us/img471/6905/ejercicio1ge4.th.jpg]

[muscleleomon]

Not sure, but they said ignoring how bouncy the balls are, so I thought that was it.

So, wouldn't it rather be inelastic? This question is pretty vague. And yeah, I think I got the direction wrong haha.

[Master Grim]

*sweat drop* Forget it. I've already got the answer.

EDIT: And I didn't really explain it too well... *sigh* I was never good at explaining...