Recent content by batballbat

ok. please delete this post.

sorry, but that is of no help. I am asking for a condition and a proof for "iff".

Homework Statement S_1 and S_2 are subsets of a vector space. When is this: span(S_1 \cap S_2) = span(S_1) \cap span(S_2) true? Prove it.Homework Equations The Attempt at a Solution conjecture: iff the two subsets are vector spaces.

i don't get it. Shouldnt a polynomial of even degree have atleast one critical point? in question 3. i meant for any odd degree we can find a polynomial which has no critical point.

Are these assertions true? I am referring to polynomials with real coefficients. 1. There exists of polynomial of any even degree such that it has no real roots. 2. Polynomials of odd degree have atleast one real root which implies that polynomial of even degree has atleast one critical...

actually this is trivial. I just learned all this the complicated way, .i.e. proving cantor bernstein without the well ordering theorem.

Is it true that: If A is not equivalent to its subset A1. Then A is not equivalent to any subset of A1?

ok thank you guys for help. But after the collision why do some objects continue in their initial direction? There is rest instance during the impact.

one final question what happens during collision? The two objects collide and are at rest for a moment when they compress. And then when they expand a force is applied to them and they move? But why not move always in opposite directions? Why does one retain its direction and the other change...

ok atleast i know that it is subtle. And now have reasons to curse some teachers and physics books. one last stupid question: When two perfectly moving bodies moving towards each other collide. How do we determine the minimum force that will push the body in opposite direction?

so perfectly elastic collision then. How do we go about solving this?

@Chestermiller thanks. any resources where i can see these calculations?

what details mfb? @arildno: Ok so the definition is not correct. Then how do we solve that puzzle? When we analyse the conservation of momentum we analyse it in terms of a force and using Newton's third law. This force should be determinable.

and answer this and then i will quit studying physics: Is the direction of the motion of bodies after collision determinable? If so, how?

So how do we determine the force? What else is required? And how do we determine the time of impact when two bodies collide? And what about the direction of their motion after the collision?