Answer:
2.9 m/s
Explanation:
Momentum will be conserved
Speed of the ball just before collision is
v = √2gh = √(2(9.8)(0.8)) = 3.96 m/s
The initial momentum is 1.3(3.96) = 5.15 kg•m/s
The block takes away momentum of 0.6(2.2) = 1.32 kg•m/s
Leaving the ball with momentum of 5.15 - 1.32 = 3.83 kg•m/s
vf(ball) = 3.83 / 1.3 = 2.946... ≈ 2.9 m/s
answer
the final velocity is half of train car B's initial velocity
explanation
the conservation of momentum states that the initial and final total momentum are equal
m1v1 + m2v2 for initial momentum
(m1 + m2)v3 for final momentum because both cars stick together so their masses are combined
m1v1 + m2v2 = (m1 + m2)v3
since the mass of both are the same, m1 = m2
m1v1 + m1v2 = (m1 + m1)v3
m1(v1 + v2) = 2m1v3
divide both sides by m1
v1 + v2 = 2v3
since train car A is initially at rest, v1 = 0
v2 = 2v3
v3 = v2 * 1/2
the final velocity is half of train car B's initial velocity
If the object doesn't move you have done no work.
