- #1
Monkeybusiness
- 3
- 0
First off - English isn't my native language, so please go easy on me if my translations are wrong.
The problem:
A ball with the mass 20g and the speed 3.0m/s collides with another ball with the mass 80g which is standing still. The collision is a sentral, fully elastic collision. Find the speed of the two balls after the collision.
I thought it was a question about the combined speed of the two after the collision, but appearently it's asking about both of the balls individual speeds after the collision.
PS: I know the answere, but I'd like to understand the equations.
The two formulas that is relevant for me (according to the book itself) is:
P(after)=P(before)
P=mv
and
E(k(after))=E(k(before))
E(k)=1/2mv^2
I'm using 'u' as the speed after the collision and 'v' as the speed before the collision.
First ball is ball (A) and the second is ball (B).
m(A)=20g=0.02kg
m(B)=80g=0.08kg
v(A)=3.0m/s
v(B)=0m/s
u(A)= unknown
u(B)= unknown
Seeking u(A) and u(B) (separately, not the combined speed)
I've tried several different setups, but the one I think I'm supposed to use is something like this:
(1) m(A)u(A)+m(B)u(B) = m(A)v(A)+m(B)v(B)
(2) 1/2m(A)u^2(A)+1/2m(B)u^2(B) = 1/2m(A)v^2(A)+1/2m(B)v^2(B)
and then switch them around, divide/multiply, and so on until I'm left with the correct equations, but I'll spare you for that now as I've failed so far. I've reached a point where I see that my equation is totally off, and I've asked quite a few of the other students, but they haven't had any luck with it either.
In advance, thanks for any tips.
The problem:
A ball with the mass 20g and the speed 3.0m/s collides with another ball with the mass 80g which is standing still. The collision is a sentral, fully elastic collision. Find the speed of the two balls after the collision.
I thought it was a question about the combined speed of the two after the collision, but appearently it's asking about both of the balls individual speeds after the collision.
PS: I know the answere, but I'd like to understand the equations.
The two formulas that is relevant for me (according to the book itself) is:
P(after)=P(before)
P=mv
and
E(k(after))=E(k(before))
E(k)=1/2mv^2
I'm using 'u' as the speed after the collision and 'v' as the speed before the collision.
First ball is ball (A) and the second is ball (B).
m(A)=20g=0.02kg
m(B)=80g=0.08kg
v(A)=3.0m/s
v(B)=0m/s
u(A)= unknown
u(B)= unknown
Seeking u(A) and u(B) (separately, not the combined speed)
I've tried several different setups, but the one I think I'm supposed to use is something like this:
(1) m(A)u(A)+m(B)u(B) = m(A)v(A)+m(B)v(B)
(2) 1/2m(A)u^2(A)+1/2m(B)u^2(B) = 1/2m(A)v^2(A)+1/2m(B)v^2(B)
and then switch them around, divide/multiply, and so on until I'm left with the correct equations, but I'll spare you for that now as I've failed so far. I've reached a point where I see that my equation is totally off, and I've asked quite a few of the other students, but they haven't had any luck with it either.
In advance, thanks for any tips.