Question

A body A of mass 1.5kg, travelling along the positive x-axis with speed 4.5m/s, collides with another body B of mass 3.2kg which, initially, is at rest. Because of the collision, A is deflected and moves with a speed 2.1m/s in a direction which is at angle 30° below the x-axis. B is set in motion at an angle θ above the x-axis. Calculate the velocity of B after the collision

Answer 1

momentum before the collision
x-direction:
p = m₁v₁ = 1.5 * 4.5 = 6.75
x-direction:
p = 0

momentum after the collision is conserved:
x-direction:
p = 6.75 = m₁v₁ + m₂v₂ = 1.5 * 2. 1* cos -30° + 3.2 * v₂*cos θ
y-direction:
p = 0 = m₁v₁ + m₂v₂ = 1.5 * 2.1 * sin -30° + 3.2 * v₂ * sin θ

Solve the two equations for v₂ and θ.