3. Each croquet ball in a set has a mass of 0.50 kg. The green ball, traveling at 12.0 m/s, strikes the blue ball, which is at rest. Assuming that the balls slide on a frictionless
surface and all collisions are head-on, find the final speed of the blue ball in each of
the following situations:
a. The green ball stops moving after it strikes the blue ball.
b. The green ball continues moving after the collision at 2.4 m/s in the
same direction.

a) v_{2f} = 12.0 m / s,  b) v_{2f} = 9.6 m / s

Explanation:

This is an exercise in conservation of momentum, let's start by defining a system formed by the two balls, so that the forces during the collision have been internal and the moment is preserved.

Initial instant. Before the crash

          p₀ = m v₁₀ + m v₂₀

where we use index 1 for the green ball and index 2 for the blue ball.

Final moment. After the crash

         p_f = m v_{1f} + m v_{2f}

the moment is preserved

         p₀ = p_f

         m v₁₀ + m v₂₀ = m v_{1f} + m v_{2f}

they tell us that the blue ball is at rest before the crash

        m v₁₀ = m v_{1f} + m v_{2f}

a) it is indicated that the green ball stops after the collision v1f = 0

        m v₁₀ = m v_{2f}

        v_{2f} = v₁₀

        v_{2f} = 12.0 m / s

b) the speed of the green ball is v_{1f} = 2.4 m / s

         m v₁₀ = m v_{1f} + m v_{2f}

         v_{2f} = v_{1o}- v_{1f}

         v_{2f} = 12.0 - 2.4

         v_{2f} = 9.6 m / s

depends on what you mean by "group." for order, it would be coleoptera (beetles). for class, it would be insecta (insects). for phylum, it would be the arthropoda (animals with jointed exoskeletons).

explanation: