Draw a diagram to illustrate the problem as shown below.
Each ball has mass = m.
The initial velocity of the blue ball = u.
The initial velocity of the red ball = 0.
Initial total momentum is
P1 = m*u + m*0 = mu
Final momentum is
P2 = mv + 3mv = 4mv
Because momentum is conserved,
mu = 4mv
u = 4v
Answer:
The velocity of the blue ball before the collision is 4v.
Each ball has mass = m.
The initial velocity of the blue ball = u.
The initial velocity of the red ball = 0.
Initial total momentum is
P1 = m*u + m*0 = mu
Final momentum is
P2 = mv + 3mv = 4mv
Because momentum is conserved,
mu = 4mv
u = 4v
Answer:
The velocity of the blue ball before the collision is 4v.