A bullet is fired with a horizontal velocity of 500 m/sec. It passes through a 3-kg block of wood, A, and becomes embedded in a second, 2.5-kg block of wood, B. The bullet causes Blocks A and B to start moving to the right with velocities of 3 m/sec and 5 m/sec, respectively. The mass (g) of the bullet is most nearly:

m = 43 g

Explanation:

Conservation of momentum.

let v be the velocity of the bullet between blocks A and B

mv + 2.5(0) = (2.5 + m)(5)

v = (12.5 + 5m) / m = 12.5/m + 5

m(500) + 3.0(0) = mv + 3.0(3)

500m = m(12.5/m + 5) + 3.0(3)

500m = 12.5 + 5m + 9

495m = 21.5

m = 0.043434343 kg

like poles repel so keep pushing north to north and repels funny to see this