- #1
SpyIsCake
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Homework Statement
Standard pool balls have a mass of 0.17kg. Before a collision, ball A is at rest and ball B is traveling at 4.5 m/s [N]. After the collision, ball B is traveling at 1.6 m/s [N20E]. What is the velocity of ball A?
Homework Equations
pinitial = pfinal
m1v1 + m2v2 = m1v1 + m2v2
The Attempt at a Solution
I believe that the initial momentum would be 0.17 * 4.5 m/s = 0.765kg m/s [N].
The momentum for B is 1.6 * 0.17 = 0.272
The initial momentum has to equal the final momentum, so:
0.765kg/m/s = 0.272 + A
I drew a triangle for B's angle.
For X component: 0.272 cos 20 deg = 0.255
For Y component: 0.272 sin 20 deg = 0.09
The X component will just be 0.255 [W] because the X component is 0.
The Y component will have to be the difference between 0.765 and 0.09302, because you need the north to have the same momentum. The answer to that is 0.7168.
Then I plug them all in and use Pythagorean theorem to find the momentum, which was 0.76 kg m/s.
I divide that by the mass of 0.17kg and got a velocity of 4.2 m/s.
But unfortunately, the answer is 3 m/s.
How?